Jelly Bean update for Galaxy S II isn’t officially available yet but through custom ROMs the phone can be updated to the very latest build of Android, version 4.1.2. The ROM we’ll be using in this guide on how to update Galaxy S II to Android 4.1.2 Jelly Bean is Paranoid JZO54K.
Note: This ROM requires an international version of Galaxy S II with ClockworkMod installed. Installing a custom ROM will void your warranty. Install at your own risk. Also make sure your all your data is backed up and your phone is fully charged.
The full guide on how to update Galaxy S II to Android 4.1.2 Jelly Bean is below.
Step 1. Download the ROM (Paranoid Android 4.1.2 JZO54K)
Step 2. Connect your phone to the computer using USB cable. Enable data transfer/mass storage mode
Step 3. Copy/Paste the downloaded file in Step 1 to the root of your mass storage drive (not in any folder)
Step 4. Disconnect the USB cable and turn off the phone
Step 5. Enter recovery mode. Do this by pressing and holding the Volume Up + Home + Power buttons.
Step 6. Use volume rocker to navigate and power button to click. Perform a data wipe + cache wipe
Step 7. Navigate to flash ZIP from SD card and choose choose ZIP from SD card
Step 8. Select the ZIP file downloaded in step 1. Select it using the power button and confirm installation.
Step 9. When installation is done, go back to the main menu of CWM and perform a reboot
You now have Android 4.1.2 on your Galaxy S II. Do note that the first boot can take up to 5 minutes