I just bought an iphone 4 with 4.0.1 on it, how do I save the 4.0.1 version of the software so if for some reason i upgrade i can still go back to 4.0.1? Do all I have to do is make a backup with itunes?
Not sure if you can still retrieve your SHSH's from Apple in order to be able to restore/downgrade to 4.0.1
You have to run tinyumbrella or JB the phone and click "make my life easier" on cydia.