Can I Re-jailbreak iPhone 4 with JailbreakMe 3.0 After Downgrading iOS 4.3.4 to iOS 4.3.3?

Hello Lionel, it’s a good thing that you have backed up your iOS 4.3.3 SHSH Blobs. Because if not, there’s a possibility that you get stuck into that firmware and wait till Apple releases the final version of iOS 5 firmware. It seems like Stefan Esser’s untethered jailbreak exploit that was utilized on Sn0wbreeze, Redsn0w, and PwnageTool will not work on iOS 4.3.4. There were reports that Apple killed the untethered jailbreak exploit on this iPhone firmware update. And because of this, the iPhone Dev Team have only managed to release a tethered jailbreak version of Redsn0w to jailbreak iOS 4.3.4. If Esser and the Dev team have managed to develop a new untethered jailbreak exploit, it is very much likely that they will release it after Apple launches the final version of iOS 5 firmware.

Anyway, you can follow this tutorial on how to downgrade iOS firmware of the iPhone, iPad, and iPod Touch. Regarding JailbreakMe 3.0, I do not think that there will be an issue if you re-jailbreak your iPhone 4 using JailbreakMe 3.0 as your iPhone 4 will run on iOS 4.3.3 firmware after the downgrade. You can follow this tutorial on how to jailbreak iPhone 4 on iOS 4.3.3 using JailbreakMe 3.0. After jailbreaking, you should install PDF Patcher 2 to patch the security flaw that was used to jailbreak your device. Developed by Comex itself, this PDF Patcher 2 will protect your device from malicious content. Also, if you are interested to unlock your iPhone again, then check this guide on how to unlock iPhone 4 on iOS 4.3.3 using Gevey Pro.