The update to KitKat 4.4 hasn’t come by way of Samsung, the update is courtesy of CyanogenMod and is for the GT-i9100 version.
This custom ROM has the name of CM11 and it is bug and bloatware free. Along with this it offers plenty of tweaks along with CM apps to install.
So if you have the Samsung Galaxy S2 GT-i9100 and you want to make the update, follow the steps outlined below.
1. Flash this firmware to the Galaxy S2 GT-I9100 only. Doing it on other models will risk bricking it.
2. Root the handset and then install a custom recovery like ClockworkMod.
3. Install the USB drivers for your Galaxy S2 on your PC.
4. Make a manual backup of all your personal info, settings and data files.
5. Ensure that your battery level is at least 50% to stop any power interruptions during the flash.
6. Enable the USB debugging mode on your phone. Head to Settings > Applications > Development > USB debugging mode or Settings > Developer options > USB debugging.
7. Download CyanogenMod 11 for Galaxy S2 i-9100 and the Google Apps package to your computer.
Flashing Instructions
1. Connect your Galaxy S2 GT-I9100 to your PC via USB.
2. Copy the CyanogenMod 11 and the Google Apps packages to the SD card of the Galaxy S2. Do not extract the zip files.
3. Unplug the phone from the PC before turning it off.
4. Reboot into recovery mode by pressing and holding the volume up, home and power keys at the same time until the Samsung logo appears.
5. Inside recovery mode, make an Android backup of your current ROM. Select “backup and restores > backup.” You can then restore the saved ROM inside the SD card anytime you need to.
6. Do a full wipe on your phone. Select “wipe data/factory reset” and “wipe cache partition.” Then choose “advanced > wipe Dalvik cache.”
7. Return to the main menu and install the CyanogenMod 11 by selecting “install zip from SD card > choose zip from SD > search the ROM you have copied earlier > confirm installation.” Do the same thing with the Google Apps.
8. Once the installation has completed, go back and select “reboot system now.”
9. It might take five minutes or so before your Galaxy S2 reaches its home screen after rebooting.
