How to Root Samsung Galaxy II i9100 4.0.3 (ICE Cream Sandwich). This method will help you for No Need Downgrade, Flash etc.
for unlocking its is necessary to root this device before unlocking
Owners of Samsung Galaxy II i9100 over Android 4.0.3,2.3.5,2.3.3, and others version who want more freedom to use their device must get access to its root, so to do that just follow the guide below.
Note: This guide only works for Windows users.
Root Samsung Galaxy II i9100 on Android 4.0.3
Requirements & Downloads:
Attach your Samsung Galaxy II i9100 to PC through USB cable and put your phone into USB Debugging mode by navigating through Settings > Applications > Development
Turn off your phone, and press Power+Volume Down and Home buttons to enter into Flash mode
(insert usb install usb drivers)
Open Odin Downloader on your computer and check mark the boxes followed by Auto reboot and F. Reset Time options in its window
Click on PDA button in Odin Downloader window, and select downloaded MyGKernelV1.1.1_CWM5.tar from your computer and click on Start button and let it do the process, it will also reboot your mobile
Enjoy, your Samsung Galaxy II i9100 is rooted so just reboot it and that is it.
Now you can unlock your Samsung Galaxy II i9100 with any Tool