i have saved my 4.3.3 with tu is it safe to try ios 5 ,the go back to 4.3.3 ?
Should be fine. My understanding is that eventually, you will have to have an older version of iTunes to continue to load/run iOS version older than iOS5+ (cause Apple is changing the way they code firmware).
Let me quote our eminent hacker, f4780y:
...[F]rom IOS5, Apple are apparently upping the ante and introducing a NONCE component into the blobs meaning they can no longer be saved and replayed later using TU, Cydia or any other method. This is one of the things they do currently to help keep the baseband protected from downgrade.
So, once Apple stop signing a version of IOS5 there will be no way to ever restore that version on your device, even if you saved your blobs, because they can only be used once.
4.x blobs will continue to work of course, provided you have them saved.
So, we'll be good to go with our iOS 4.3.3 blobs - but will not be able to use blobs for 5.x and higher after iOS 5 is released. Will be interesting to see what can/will be done...
Yeah, I know, more than you asked for, but I just have to remind people that iOS 5 is going to be a v-e-r-y different ballgame for jailbreakers...
Marilyn