I have a jailbroken iPhone 4 on firmware 4.2.1 It's acting whacky today after a Cydia update. Cannot find the cause despite installing and uninstalling Cydia apps. Looks like I may have to reset the iPhone and rejailbreak. Thing is, I don't want to upgrade from 4.2.1 Big reason is, tethering. AT&T seems to have tougher time snooping around with people who have 4.2.1 Whether that is true or not.... Can I simply download a 4.2.1 IPSW file and in iTunes have it update that firmware rather than the newest one? If that can be done, can someone take a moment and post step-by-step instructions to doing it including the specific right-click iTunes command to manually update the phone? Again, I want to reset iPhone and have it install iOS 4.2.1 Hopefully it can be done. Then I can rejailbreak with GreenPoison.