Hi all, I have a special situation with an iPhone that I wanted to ask about. A friend of mine got a used iPhone from his Aunt as a Christmas gift. The Aunt purchased the phone around September so I believe it had 1.0.2 firmware on it originally. She had a legit AT&T account on the phone and upgraded firmware as she went, so the phone now has 1.1.2 firmware on it. My friend has a T-Mobile account and would like to use his new iPhone.

My iPhone started out with 1.0.2 firmware and I have upgraded to 1.1.2 and unlocked. I'm on T-Mobile so that's why he wants me to unlock his phone. However, my phone has never been activated through AT&T, so I'm not sure if it's a different situation. My questions are:

1) How would I go about unlocking a legit AT&T phone to use with T-Mobile?
2) Is there a way I can revert the phone back to factory 1.1.2 firmware later if he wants to go with AT&T?

Thanks in advance