Samsung Galaxy S2 users update their device to Android 4.1.2 using RootBox Custom ROM. This is not an official Android 4.1.2 ROM by Samsung.
Features of Rootbox Android 4.1.2
Based on JB 4.1.2 – Built from RootBox Sources
Cherry picked fixes from CM
ExTweaks integrated in Settings – if ExTweaks installed in /system/app
To use the Custom ROM you require a rooted device. You can check if your device is rooted by installing Root Checker from Google Play. RootBox ROM is in development stage so you may experience bugs. As per the developer HWcomposer is not working and there is no option to swap Internal/External.
The guide mentioned below is only for Samsung Galaxy S2 I9100 and not for any other device. You can check your device model number by going to Settings >> About Phone.
We cannot be held liable of any damage done to your device while following the below mentioned procedure.
Install Android 4.1.2 on Galaxy S2 using RootBox Custom ROM
Take a complete backup of data,apps and settings as the procedure may wipe your data.
Make sure that the battery of device has a minimum charge of 60%.
Enable “USB debugging” on your device by going to Settings >> Developer options >> Enable USB debugging.
Download RootBox ROM from here and Google Apps Package from here.
Copy both the zip files to SD-Card of your device without extracting.
Switch off device and enter into recovery mode. To enter recovery press and hold the Volume Up and Volume Down and Power buttons.
Take a Nandrop back up of your existing ROM. Select Backup and Restore option from the recovery mode and then select backup again.
Select “wipe data/factory reset” and confirm to wipe all data. Wipe “Dalvik Cache”.
Select “install zip from sdcard” and then select “choose zip from sdcard”. Navigate to RootBox ROM file and select to install. Wait till installation is complete.
Repeat the procedure to install Google Apps Package.
Select “go back” and then select “reboot system now”.
Android 4.1.2 Jelly Bean on Galaxy S2 with RootBox ROM is installed.