4.2.1 downgrade to 4.0 iPhone 4

[invisiblelight]

Friends,

Scoured around the forums and didn't find exactly what I am looking for. I made the jump from the pocket PC ph ones to iPhone this last summer, so a lot of this is new.

I am able to figure out how to jailbreak w/no problems. At present I am using 4.2.1 jailbreak greenpoison. When the iPhone 4 was releases I was able to jailbreak via jailbreak me web site. It seemed at the time upgrading to 4.2.1 was actually not beneficial but did it anyways.

I know it's possible to go back to iOS 4 but how does apple iTunes look at it? Will it block my phone from registering and sync'ing after the downgrade? What r the repercussions?

Also since I am new and catching onto these hacking tools and terms. What would I need to perform this operation?

Please advise and thank you

tvos

[Trees415]

Why would you want to go back to 4.0? The way I see it, you'd be better off staying at 4.2.1, given the new features, faster OS, etc.