iTunes Error 2 when Restoring Stock iOS 4.3.5

Hello Oscar, it seems like the application support for iTunes is missing and this is the reason why you are getting error when restoring stock iPhone firmware. Anyway, to fix iTunes error 2, all you need to do is uninstall iTunes on your computer and download and install the latest version of iTunes. You can download iTunes 10.4 in Apple’s official website using this link. And you can check this blog post to know more about iOS 4.3.5 as well as download the firmware from here.

Regarding jailbreak iOS 4.3.5, you will be able to jailbreak it using Redsn0w 0.9.8b4. However, it is worth noting here that there’s no untethered jailbreak support on iOS 4.3.5 primarily because Apple already patched the exploit on this version of firmware. Meaning, you will only get tethered jailbreak on iOS 4.3.5 where you will need to connect your iPhone to your computer and boot it into tethered jailbroken state every time you power off or reboot your device. 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.

If you want to get untethered jailbreak, then you can downgrade your iPhone back to iOS 4.3.1, iOS 4.3.2 or iOS 4.3.3 by creating a signed IPSW using iFaith SHSH Blobs Dumper. However, this process is only possible if you have previously installed these firmwares on your device. If you have installed all of these firmwares, then I would recommend you to downgrade to iOS 4.3.3 and jailbreak it using JailbreakMe 3.0.