How can I downgrade my iPhone from firmware 1.1.1 to 1.0.2 or earlier?
Since Apple released iPhone firmware update 1.1.1, there has been a lot of griping and complaining about Apple "re-locking" the iPhone. Users with SIM unlocked iPhones have had their phones bricked, while those who installed third party enhancements and applications on their iPhone have had these applications rendered useless.
Thankfully, thanks to a user in the Hackint0sh forums, a method of downgrading your iPhone firmware (previously thought to be impossible) is now available.
iPhoneAtlas, another iPhone-dedicated site, has done a great job of fleshing out the instructions provided on the forum into a set of detailed, easy to follow instructions. Rather than rehash them here, just head to iPhoneAtlas for the details.