The AT&T iPhone 4 I purchased back on launch day is still running, despite being dropped into a puddle of water some time ago. I’ve gotten a lot of use out of it, and it’s truly a terrific phone.
Today I finally updated the phone from iOS 4.0 to iOS 4.2.1. Since I’m living in Vietnam, it’s a requirement that the phone be unlocked, and I wanted to wait until I was 100% sure I could update the phone successfully.
The other reason is that I had chosen the “Reset All Content and Settings” option in the Settings app, before learning that this process can take many hours– and still fail to work. Doing a restore using PwnageTool 4.2 was quite straightforward, provided I have the right .bundle and .ipsw files.
After restoring the phone, I needed to run Cydia and re-install ultrasn0w. That did the trick; the phone is now working perfectly, running iOS 4.2.1, and having none of my old data on it 
not really perfectly
need to work on it more. connection is not that good. Sometime it does not work that well.
How to unlock my Iphone 4 Version 4.2.1 it was been jailbreaked and send to India but now i need to unlock it. Please advise