Despite being a 4-year-old handset, the Galaxy S3 gets Android 7.0 Nougat with unofficial CyanogenMod 14 custom ROM. The last official firmware that Samsung released for Galaxy S3 is I9300XXUGOE1, which is based on Android 4.3 Jelly Bean. Thanks to the large developer community, a working port of Android 7.0 Nougat based unofficial CM 14 custom ROM is now available for Galaxy S3, which means you can still enjoy the latest features of Android OS on your good old device.
Unfortunately, a fully working port of Android 7.0 Nougat based custom ROM is not yet available for Galaxy S3. Most of them are initial builds and facing issues with RIL, Wi-Fi tethering and video recording. Here are two unofficial CyanogenMod 14 custom ROMs for Galaxy S3 (i9300/ i9305) with most things working, but both are still a testing version and cannot be used as a daily driver.
Interested Galaxy S3 owners may go through the easy installation guide given below to install the unofficial CyanogenMod 14 (Android 7.0 Nougat) on Galaxy S3 i9300 (international variant) and S3 LTE i9305.
Note: The below given files are testing version, which means it contain several bugs. In addition, as they are initial builds, you may not get all the features of Nougat and CyanogenMod.
Note: We are assuming that you have already rooted your Galaxy S3 and installed latest version of TWRP recovery on it.
Note: Before you start, make sure you have a stock system image to flash back to. Make a system backup from TWRP recovery before proceeding.
Disclaimer: Please follow this guide at your own risk. Though we are putting our level best to provide this tutorial at its maximum perfection and accuracy, we can’t take responsibility for anything that goes wrong. This guide is intended for technically talented users only.
2. Save both CM14 ROM zip file and Gaps zip file to your S3’s SD card.
3. Reboot your Galaxy S3 to TWRP recovery. To do so, press and hold Volume Up, Home, and Power button few seconds.
4. In recovery, perform a full wipe (cache, dalvik cache, data/factory reset) by selecting ‘Wipe’ option.
5. Now, flash CM14 and Gapps. To do so, select ‘Install’, navigate to ROM zip file and swipe to confirm flash. Repeat the same for Gapps as well.
6. Before rebooting, once again wipe cache partition and data, and then reboot your phone.