Most people assume an old Android phone becomes useless once it stops receiving official updates. Apps stop working properly, security patches disappear, and performance gets worse every year. Eventually the phone ends up forgotten in a drawer.
But what if that same 8-year-old phone could run Android 15 — the latest version of Android?
In this guide, I’ll show you exactly how I revived my old Xiaomi Redmi Y1 Lite (2017) and installed Android 15 using LineageOS, a powerful open-source custom ROM maintained by the Android community. This phone originally shipped with Android 7 and stopped getting updates years ago. Now it runs modern apps, the Play Store works perfectly, and the device feels usable again.
If you have an old Android phone lying around, don’t throw it away. Follow this step-by-step tutorial and give your device a second life.
Let’s get started.
Before You Begin (Important Information)
Before we jump into the installation steps, there are a few important things you should understand. Installing a custom ROM is safe when done correctly, but it’s not the same as installing a normal app. You’ll be modifying the phone’s system software, so preparation matters.
What You’ll Need
- A Windows PC or laptop
- A USB cable that supports data transfer
- At least 50% battery on your phone
- A backup of your important data
- The exact LineageOS files for your device
This process will erase everything on your phone, including photos, apps, and accounts. If there’s anything important on the device, back it up first.
Compatibility Check
Not every phone supports Android 15 through LineageOS. Some devices have active developer support, while others don’t. The success of this installation depends entirely on whether your device has an official or well-maintained LineageOS build.
Always download ROM files from the official LineageOS website for your specific device model. Using the wrong files can cause boot loops or make the phone unusable.
Risk Disclaimer
Unlocking the bootloader and installing a custom ROM:
- May void manufacturer warranty
- Can brick the device if done incorrectly
- Is done entirely at your own risk
That said, if you follow the instructions carefully and use the correct files, the process is very reliable — especially for older phones like the Redmi Y1 Lite.
Now that everything is clear, let’s prepare your computer for the installation.
Step 1: Install ADB & Fastboot (Platform Tools)
To install Android 15, your computer needs tools that can talk to your phone at a system level. These tools are called ADB and Fastboot, and they’re part of Google’s official Android Platform Tools package.
ADB lets your PC send commands while Android is running.
Fastboot works when the phone is in bootloader mode.
Both are required for flashing LineageOS.
First, download the Platform Tools from Google using the button below:
After downloading:
- Extract the ZIP file
- Move the extracted folder somewhere easy to access
(Example:C:\platform-tools)
Now we’ll make sure Windows can use ADB from anywhere.
Add Platform Tools to System PATH
- Copy the folder path of platform-tools
- Search ENV in Windows search
- Open Edit the system environment variables
- Click Environment Variables
- Under System Variables → select Path → click Edit
- Click New → paste the folder path
- Press OK to save everything
Test if ADB Works
Open Command Prompt and type:
adb --version
If you see a version number, ADB is installed correctly and ready to use.
Next, we’ll install the USB drivers so your PC can properly detect the phone.
Step 2: Install Google USB Driver (Windows)
Now we need to make sure your computer can properly detect the phone — especially in fastboot mode. Without the correct USB driver, ADB and Fastboot may fail to recognize your device.
Google provides an official USB driver package that works with most Android devices on Windows.
Download it using the button below:
After downloading:
- Extract the ZIP file
- Open the extracted folder
- Find the file named android_winusb.inf
- Right-click it → choose Install
Windows may show a security warning — click Install anyway.
Once installed, reconnect your phone to the PC.
Quick Driver Test
Open Command Prompt and run:
adb devices
If your phone appears in the list (after accepting the prompt on your phone), the driver is working correctly.
Next, we’ll download the LineageOS ROM and recovery files for your device.
Step 3: Download LineageOS ROM & Recovery Files
Now it’s time to download the actual Android 15 system files for your phone. These come from the official LineageOS website. Every supported device has its own dedicated page with ROM builds, recovery images, and installation instructions.
It’s extremely important that you download files only for your exact phone model. Flashing the wrong ROM can cause boot loops or permanently brick the device.
Open the official LineageOS website using the button below:
Then follow these steps:
- Click Get LineageOS
- Search for your phone model
- Open your device page
- Download:
- The latest LineageOS ROM ZIP
- The LineageOS Recovery IMG
- Open the Installation tab on that same page
(this contains device-specific instructions)
For my device (Redmi Y1 Lite), the latest version available is LineageOS 22.x based on Android 15.
Organize Your Files
Create a simple folder like:
C:\lineage
Place the ROM ZIP and recovery IMG inside this folder. This makes flashing easier in the next steps.
Next, we’ll prepare the phone by enabling Developer Options and USB Debugging.
Step 4: Enable Developer Options & USB Debugging
Before your computer can send commands to the phone, you need to enable a hidden settings menu called Developer Options. This unlocks USB debugging, which is required for flashing the ROM.
On your phone:
- Open Settings
- Go to About phone
- Tap Build Number 7 times quickly
→ You’ll see a message: “You are now a developer”
Now go back:
- Open Developer Options
- Turn on USB Debugging
When you connect your phone to the PC later, Android will ask for permission. Always tap Allow.
Important Safety Step
Before unlocking or flashing anything:
- Remove all Google accounts
- Remove screen lock (PIN/password/fingerprint)
- Disable Find My Device if enabled
This prevents Factory Reset Protection (FRP) from locking your phone after formatting.
Now the phone is ready to communicate with your PC.
Next comes the most important requirement: unlocking the bootloader.
Step 5: Unlock the Bootloader
Unlocking the bootloader is required before installing any custom recovery or ROM. Think of the bootloader as a security lock placed by the manufacturer. Until it’s unlocked, the phone will refuse to install unofficial software like LineageOS.
⚠️ This step will completely wipe your phone.
Every manufacturer uses a different bootloader unlock method:
- Xiaomi → Mi Unlock Tool
- Motorola → Unlock code from Motorola website
- Samsung → OEM unlock (varies by region/model)
- Realme / Oppo / Vivo → Brand-specific procedures
- Google Pixel → Fastboot command unlock
Because the process is different for every device, there is no universal guide that works for all phones.
👉 You must follow the official bootloader unlock instructions for your exact device model.
For my Redmi Y1 Lite, I used Xiaomi’s Mi Unlock Tool and completed the unlock process before continuing.
Once your bootloader is unlocked, come back and follow the next steps.
Step 6: Connect Phone to PC & Verify ADB Connection
Now that the bootloader is unlocked and USB debugging is enabled, we’ll confirm that your computer can properly communicate with the phone.
- Connect your phone to the PC using a USB cable
- Open Command Prompt on your computer
- Type the command:
adb devices
On your phone, a message will appear asking:
“Allow USB debugging?”
Tap Allow and check Always allow from this computer.
If everything is working correctly, your device ID will appear in Command Prompt. That means ADB is successfully connected.
If no device appears:
- Reconnect the cable
- Try a different USB port
- Reinstall the USB driver
- Enable USB debugging again
Once ADB is working, we’ll reboot the phone into fastboot mode.
Step 7: Boot Into Fastboot Mode
Fastboot mode is a special low-level mode that allows your PC to flash system partitions like recovery and ROM images.
You can enter fastboot in two ways.
Method 1: Using ADB command
In Command Prompt, type:
adb reboot bootloader
Your phone will automatically restart into fastboot mode.
Method 2: Hardware buttons
- Power off the phone completely
- Hold Volume Down + Power together
- Keep holding until the fastboot screen appears
Once in fastboot mode, confirm detection:
fastboot devices
If your device ID appears, fastboot is working correctly.
If nothing shows:
- Reinstall USB drivers
- Try another USB port
- Change cable
Now that fastboot is ready, we can flash the LineageOS recovery.
Step 8: Flash LineageOS Recovery
Now we’ll replace the stock recovery with LineageOS Recovery, which is required to install the ROM.
Make sure the recovery image you downloaded is inside your Lineage folder (example: C:\lineage).
- Open the Lineage folder
- Hold Shift + Right Click inside the folder
- Choose Open Command Window here (or Open Terminal here)
Your phone must still be in fastboot mode.
Flash the recovery using:
fastboot flash recovery lineage-22.2-recovery.img
(Replace the filename with your actual recovery file name.)
After flashing completes, boot directly into the new recovery:
fastboot reboot recovery
⚠️ Important: Boot into recovery immediately after flashing.
If you reboot normally, the system may overwrite the custom recovery.
You should now see the LineageOS Recovery screen.
Next, we’ll wipe the device and prepare it for a clean Android 15 install.
Step 9: Factory Reset (Clean Install Required)
Before installing the new Android system, we must wipe the old data. This prevents crashes, bootloops, and compatibility issues.
Inside LineageOS Recovery:
- Select Factory Reset
- Choose Format data / factory reset
- Confirm the action
This step completely erases the old Android system and user data. It gives LineageOS a clean environment to install.
After formatting:
- Go back to the main recovery menu
Now your phone is empty and ready to receive the Android 15 ROM.
Next, we’ll sideload the LineageOS ROM from your computer.
Step 10: Install LineageOS (Android 15) via ADB Sideload
Now we’ll send the Android 15 ROM from your PC to the phone.
On the phone (inside LineageOS Recovery):
- Select Apply Update
- Choose Apply from ADB
The screen will say the device is ready to receive files.
Now on your computer:
Open Command Prompt in the folder where your ROM ZIP is saved.
Run:
adb sideload lineage-22.2-xxxxx.zip
Replace the filename with your actual ROM file name.
The progress will slowly move from 0% to 100%. This may take several minutes — do not disconnect the cable.
When finished, the ROM is installed.
⚠️ Do NOT reboot yet if you want Google apps.
Next, we’ll install Play Store and Google services.
Step 11: Install Google Apps (Play Store & Services)
LineageOS does not include Google apps by default. If you want the Play Store, Gmail, Maps, and Google services, you must install a compatible GApps package right after flashing the ROM.
Make sure you download a GApps package that matches:
- Android version → Android 15
- Architecture → usually ARM64 (check your device)
- Compatible with LineageOS
Place the GApps ZIP file in the same folder as your ROM.
On the phone:
- Choose Apply from ADB again
On your PC:
adb sideload gapps-package.zip
Replace the filename with your actual GApps ZIP.
During installation you may see:
Signature verification failed
This is normal — choose Yes to continue.
Wait until installation completes.
Now everything is ready for the first boot.
Step 12: First Boot Into Android 15
Now you can finally boot into your new system.
In LineageOS Recovery:
- Select Reboot system now
The first boot takes longer than normal — sometimes up to 5–10 minutes. This is expected. The system is building caches and preparing Android for the first time.
⚠️ Do not interrupt this process.
Do not press buttons.
Do not disconnect power.
Just wait patiently.
After booting, you’ll see the Android setup screen.
- Connect to Wi-Fi
- Sign in to your Google account (if GApps installed)
- Finish the setup wizard
Once setup is complete, open:
Settings → About phone
You should see Android 15 listed.
Your old phone is officially running the latest Android.
Troubleshooting & Common Fixes
If something doesn’t work the first time, don’t panic. Most installation problems are easy to fix.
❌ Phone not detected by ADB
Problem: adb devices shows nothing
Fix:
- Reconnect USB cable
- Accept USB debugging popup again
- Enable USB debugging again
- Try another USB port
- Reinstall Google USB driver
❌ Fastboot not detecting device
Problem: fastboot devices returns blank
Fix:
- Reinstall USB driver
- Use a different cable
- Try USB 2.0 port instead of USB 3.0
- Restart PC and try again
❌ Bootloop after flashing
Problem: Phone keeps restarting
Fix:
- Go back to recovery
- Do Factory Reset again
- Reflash ROM
- Make sure you used the correct device files
Most bootloops happen because the data partition wasn’t wiped.
❌ No Play Store after install
Problem: ROM installed but no Google apps
Fix:
- You skipped GApps installation
- Or installed wrong Android version GApps
- Reboot to recovery → sideload correct GApps
Final Result
You just installed Android 15 on an unsupported 8-year-old phone.
A device stuck on Android 7 is now:
✅ Running modern Android
✅ Receiving community security patches
✅ Compatible with new apps
✅ Smooth and usable again
✅ Perfect as backup phone / media device / GPS / kids phone
This is the power of open-source Android and community development.
Instead of throwing old hardware away, you gave it a second life.
If you have another old phone, you can repeat the same process — just use the correct LineageOS page for that model.
