Any Body Tell Me???And Help Me?
 

i have iphone 3gs..fw version 3.1.3.. when i update 4.2.1...this fw version update successful....but when i jailbreak via redsn0w....showig display is ok...i can'n understand .when i phone off after phone On...showing dis just Apple logo............phone is stuck in apple logo............ any solution on this method.....? Any Body full Guide me....how to downgrade in.....4.1.2 to 4.0/4.1............
plz plz help me????????????