[Q] Need help to root my samsung galaxy s2

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http://forum.xda-developers.com – This is my new first android phone Samsung galaxy s2 I9100 Device info: Build number:GINGERBREAD.XWKF3 Kernal Version: I9100 XWKF3 Android version 2.3.3 I have few questions: 1)Need procedure to root my device and install the custom ROM.. 2)Which ROM is best? 3)can i back up my OS so that in case i need to revert back. And finally i am a noob so details step by step procedure will be helpfull thanks Thanks. (HowTos)