The firmware files provided in this guide are meant for Galaxy S3. Do not install this ROM on any other device or incorrect variant. To check out what device you have, go to Settings > More/General > About Device or Settings > About Device.
UnlockRoot will not be liable for any damage occurred to your phone during or after the installation of Android 7.1 Nougat CM14.1 ROM. Proceed at your risk.
Before Getting Started:
- Make sure that your Galaxy S3 has at least 80% battery charge to avoid unexpected device shutdown while installing the ROM
- Back up data and settings using a recommended custom recovery tool, like ClockworkMod (CWM) or TWRP. In case anything goes wrong then you’ll be able to restore your data back.
- Download and install the correct USB drivers for the phone on your PC.
- Enable USB Debugging mode via Settings > Developer Options.
- Your Galaxy S3 must be rooted with custom recovery (TWRP or CWM) installed via Hiemdall or Odin and its bootloader is unlocked.
- Android 7.1 CyanogenMod 14.1 ROM for Galaxy S3 I9300
- Google Apps (Nano)
Steps to Install Android 7.1 CyanogenMod ROM on Galaxy S3 I9300:
Step 1: – First, download Android 7.1 CyanogenMod 14.1 custom ROM and Google Apps package on the desktop of your computer for Galaxy S3.
Step 2: – Connect your phone to the PC using USB data cable and mount its USB mass storage.
Step 3: – Move the downloaded CyanogenMod ROM zip file to the root folder on the root folder of your SDcard of S3.
Step 4: – Turn OFF the phone and disconnect its USB cable from computer.
Step 5: – Turn ON the Galaxy S3 in order to boot into Recovery Mode by pressing Volume up, Home and Power buttons at the same time on your phone until the Samsung screen appears.
Step 6: – While your phone is now in recovery mode, perform a “full data wipe” task by selecting Wipe Data/Factory Reset. Also, perform Wipe Cache Partition and wait until the process completes.
Step 7: – It is also recommended to perform Wipe Dalvik Cache by navigating to the ‘advanced’ option and then click Wipe Dalvik Cache. This will help to prevent boot loop issues or any boot ROM related errors during firmware installation.
Step 8: – Go back to the main menu of recovery and choose Install Zip from SD card.
Step 9: – Select Choose Zip from SD card. Locate the CyanogenMod ROM zip file that you have already copied to your phone’s SD card, select it and confirm the ROM installation on the next screen to begin.
Step 10: – Repeat the above steps to install Google Apps (Gapps).
Step 11: – Once both the ROM and Gapps are installed, choose “+++++Go Back+++++” and select Reboot System Now in the Recovery menu.
The phone will now reboot and it will take about 4-5 minutes while booting for the first time after installation.
That’s All! You have successfully updated your Galaxy S3 GT-I9300 to the latest Android 7.1 Nougat update via CM14.1 custom ROM.[Source: XDA]