thanks for the answer.
firmware is different than the android version? what I mean is should I go ahead and backup using 4EXT, update the firmware, install the ARHD ICS ROM, restore my 4EXT backup and it should go fine?
Sorry If I ask too much but I just want to make sure, it's a big deal for me, and it's a noob friendly thread
If you restore 4ext backup after ARHD flashing , it will overwrite everything except firmware. So you will lose ARHD and get back your stock. This may lead to bootloop as the new firmware is still there. Please do read about nandroid backup.
Here is the thread where you will get all preleminary know how and important links.
http://xdaforums.com/showthread.php?t=1480061
Hope this makes you clear.