HOW TO: Install XWLST Android 4.1.2 on Galaxy S2 I9100 Stock Firmware Update

Samsung Galaxy S2 users in the region of India and countries around it received this latest XWLST Android 4.1.2 Jelly Bean official firmware update a few days back that brings this phone up to date with the latest changes made by Samsung in the Android 4.1.2 software update. Don’t really expect any new features if you had already received the Jelly Bean firmware update because there is nothing new other than the usual bug fixes and minor changes that none of us will notice. This is a safe method to install I9100XWLST because it is an official firmware, not a modified or a custom ROM. You can easily install XWLST Android 4.1.2 Jelly Bean on Galaxy S2 I9100 using the tutorial given below — and also root XWLST Android 4.1.2 firmware!
Disclaimer:

This guide will be using ‘Odin’ as a tool to flash the official firmware on your Galaxy S2 I9100. During the process, you might lose all your existing installed apps and personal settings. It is therefore necessary for you to follow the guide carefully. Also, please, do mind that this tutorial is only for Galaxy S2 I9100. Don’t try this guide in any other Android device.

Steps to install Android 4.1.2 XWLST Jelly Bean update on Samsung Galaxy S2 I9100
Step-1: Download Android 4.1.2 I9100XWLST Jelly Bean official update for Samsung Galaxy S2 to the computer   
Step-2: Extract the downloaded zip to get a file with .tar.md5 extension along with few other files   
Step-3: Download Odin 3.07 which will help to install Jelly Bean firmware on the phone. Extract the zip to get Odin3 v3.07.exe and some other files    
Step-4: Switch off the Galaxy S2. Now place the device into Download Mode by pressing and holding Volume Down and Home buttons together and then press the Power button until the construction Android robot and a triangle is seen on the screen. Press the Power button again to continue to enter into Download Mode           
Step-5: Launch Odin on the computer as an Administrator     
Step-6: Connect the phone to the computer using USB cable while it is in the Download Mode. Wait until Odin detects the phone. When the device is connected successfully, the ID: COM box will turn yellow with COM port number. Also, the successful connection will be indicated by an Added message in Odin.
If the Added message does not appear, then try the USB port at the back of the computer. If that too does not work, then re-install USB driver
Step-7: Select these files extracted from I9100XWLST folder to install on the phone
a) Click on PDA button and select the file with .tar.md5 extension
b) Click on Phone button and select file with MODEM in its name
c) Click on CSC button and select file with CSC in its name
d) Click on PIT button and select the .pit file
Note: Ignore the last three steps (b, c and d) in case such files are not found.
Step-8: In Odin ensure the Auto Reboot and F.Reset Time checkboxes are selected. But uncheck the Re-Partition option; select it only when a .pit file is being used
Step-9: Click the Start button in Odin. The installation process should begin now and would take a few minutes to complete          
Step-10: Once the installation process is completed, the phone will restart automatically. Also, a PASS message with green background will appear in Odin indicating successful installation. After the home screen is seen on the phone, unplug the USB cable from the device to disconnect it from the computer
Android 4.1.2 XWLST Jelly Bean official firmware is now installed and running on Samsung Galaxy S2 I9100. Navigate to Settings>> About Phone to verify the new software version of the device.
Galaxy S2 users who have already updated their devices with the latest official build may follow our step-by-step guide to root the same.
Steps to root Samsung Galaxy S2 I9100 on Android 4.1.2 XWLST Jelly Bean
Step-1: Download root kernel for Samsung Galaxy S2 to the computer
File name: Siyah-s2-v6.0b4.tar
Step-2: Download Odin v1.85 which will help to root the Jelly Bean firmware
Step-3: Power off the Galaxy S2 and boot the device into Download Mode. Press and hold Volume Down and Home buttons together then press the Power button until the construction Android robot and a triangle is seen. Press the Power button to confirm to enter Download Mode         
Step-4: Open Odin on the computer
Step-5: Connect the Galaxy S2 to the computer while it is in the Download Mode
Step-6: In Odin, click on PDA button and select the Siyah-s2-v6.0b4.tar file 
Step-7: Verify that the Auto-Reboot and F.Reset Time options are selected in Odin
Step-8: Click the Start button in Odin to begin installation
Step-9: Once the installation process is completed, the phone will restart automatically. Disconnect the phone from the computer after the home screen is seen on the device    
Samsung Galaxy S2 running on Android 4.1.2 XWLST Jelly Bean should now be rooted successfully. Open the app drawer of the device and look for an app called Superuser from the list. Also, verify the root status of Galaxy S2 by downloading Root Checker app from Google Play Store.