[shivamrox]

i got a iphone 3g 2.2.1. so i got another on 2.1 one which i want restore with the others back up so when i do click to do that it comes that it has ahigher version does that mean i have to go to ver 2.2.1 only to restore the first iphone's backup or it can also happen with the ver 3.0

[Robcoffee]

Backups can only go forwards not backwards, so if your backup is 2.2.1 it will only synch with 2.2.1 firmware or 3.0 firware. So your 2.1 3g will need to be upgraded to 2.2.1 or 3.0 to use the backup with iTunes, or if you have both jailbroken you could SSH the relevant information out of the 2.2.1 iphone and the SSH it back into the 2.1 iphone.