Android 5.1.1 offers significantly better security patches than Jelly Bean.
Because official update servers no longer support this legacy hardware, third-party firmwares hosted on independent developer communities are the only path to modernizing the operating system. Prerequisites & Preparation
You will need the following files to update your device. These are usually found on XDA Developers forums or specialized custom ROM websites.
Storage Space: The GT-I9100 has a small system partition. If GApps fails to install, use the "Pico" version to save space.
In TWRP:
Be patient.
: Ensure at least 60% charge to prevent a shutdown during the flashing process.
| Problem | Possible Cause | Solution | | :--- | :--- | :--- | | | The ROM isn't compatible with your specific phone model. | Double-check you are using the correct file for the GT-I9100. | | Phone Stuck in a "Bootloop" | Something went wrong during installation. | Boot back into TWRP, perform a full wipe again (step 2 in Installation Method 2), and re-flash the ROM and GApps. Ensure you did the "Factory Reset" (wipe data) step. | | GApps Installation Error | You didn't wipe the system partition before installing. | The most common cause is not performing the factory reset. Boot into TWRP, wipe the required partitions, and flash the ROM and GApps again. | | "No Root" Access | Root is disabled by default in some ROMs. | Enable it in Developer Options as described in the previous section. | | Wi-Fi Not Working | A software glitch in that specific ROM build. | Try going into Settings > Backup & Reset > Network settings reset . If that fails, you may need to try a different build or alternative ROM. |
Disclaimer: Installing custom firmware is done at your own risk. This process voids your warranty and can damage your device if not followed correctly. If you'd like, I can:
Since there is no "official" 5.1.1 firmware from Samsung, you will need two specific ZIP files: Custom ROM (CyanogenMod 12.1 / LineageOS 12.1)
Download the "Pico" or "Nano" package for Android 5.1 (ARM) from OpenGApps .
You will need three specific files moved to your phone's internal storage or SD card: Search XDA Developers for " Android 5.1.1 ROM" (e.g., CyanogenMod 12.1).
The Samsung Galaxy S2 (GT-I9100) Go to product viewer dialog for this item.
Focused on shedding unnecessary framework weights to run flawlessly on devices with lower RAM footprints like the S2.