Is it Possible to Restore iPhone 3GS From iOS 4.1 to iOS 4.3.3?

Hello Douglas, this process is possible if your iPhone 3GS was jailbroken before and you have saved iOS 4.3.3 SHSH blobs which was created using TinyUmbrella, iFaith SHSH Blobs Dumper, Cydia or iSHSHit. If not, then there’s no way you will be able the upgrade as well as downgrade your iOS device to iOS 4.3.3 due to the fact that apple already stopped signing this firmware. If you aren’t aware, the Cupertino, California-based iPhone maker already stopped signing the iOS 4.3.3 firmware in order to prevent iOS device users – especially iPad 2 users – to jailbreak their devices using the new JailbreakMe 3.0, which is the easiest and fastest way available to jailbreak an iPhone, iPad, and iPod Touch running on iOS 4.3.3.

Anyway, if you want to update your iPhone, iTunes will restore your iOS device to iOS 4.3.5. Then you can jailbreak it using Redsn0w jailbreak tool which is available for both Windows and Mac OS X users. The step by step guide on how to jailbreak iOS 4.3.5 using Redsn0w 0.9.8b4 can be found on this blog post. However, you should be noted that the untethered jailbreak exploit used on iOS 4.3.1 up to iOS 4.3.3 is not working on this firmware. Meaning, you will only get tethered jailbreak, in which you have to connect your iPhone to the computer and power it on using Redsn0w.