Here I shared with you CyanogenMod 12.1 custom firmware based on Android 5.1 Lollipop for HTC’s 2014 flagship. The Lollipop custom ROM is now also available for Samsung Galaxy S3 I9300. Here is how to update Galaxy S3 I9300 to Android 5.1 Lollipop based CM 12.1.

Prerequisites to update Galaxy S3 i9300 to Android 5.1 CM 12.1:  

• Create a backup of all important data in your Galaxy device.
• Download and install USB drivers for Samsung Galaxy S3 in your computer.
• Enable USB debugging option by pressing Menu > Settings > Applications. Navigate and tap on Developer Options to ensure that USB Debugging is enabled.
• Make sure that recovery tool like ClockworkMod recovery is installed.
• Ensure that your Samsung Galaxy S3 i9300 carries more than 80% of charge. 
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Update Galaxy S3 i9300 to Android 5.1:

Files required: download the CM 12.1 Android 5.1 Lollipop custom firmware from here;  also download the Google Apps. Save both files on PC.

1. Here are the steps to update Galaxy S3 i9300 to Android 5.1 based CyanogenMod 12.1:
2. Connect your Samsung Galaxy S3 I9300 to your computer using USB cable and copy the downloaded files to the SD card of your Galaxy device.
3. Disconnect the connection with PC and turn your Galaxy S3 off.
4. Boot in to custom recovery mode: press and hold Volume Up, Down and the Power buttons simultaneously until Samsung logo shows up. Leave the keys for half a second and hold again. Use Volume keys to scroll and Power button to select – alternatively you can use Quick Boot app to reboot your Android device in recovery mode.
5. Now perform Nandroid backup of your current ROM: select Backup and Restore > Backup. Go back to main recovery menu after backup process is done – very important step to restore back to current OS.
6. Data wiping tasks: select wipe data/factory reset > Yes. It will take a few minutes; once done, select wipe cache partition. Next tap on Advance > wipe Dalvik Cache to wipe Dalvik cache data too.
7. Select install zip from sdcard followed by choose zip from sdcard. Locate the Android 5.1 based CM 12.1 custom ROM file copied earlier and select it. Tap on yes to confirm installation and wait for the ROM installation to be completed.
8. Once installation process is finished successfully, repeat the above step but choose GApps file instead to install the Google apps package on your SGS3 I9300.
9. Return to main recovery menu now and select reboot system now to boot up into the latest CM 12.1 Android 5.1 Lollipop custom firmware for Samsung Galaxy S3. It will take a bit of time during the first boot, so kindly be patient.
10. Ta da! Enjoy Lollipop on Galaxy S3.

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How to restore: If you want to return to previous OS on your SGS3, boot into recovery, select backup and restore then restore your previous ROM by selecting it from the list.

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