This guide explains how to update your iPhone 4 to iOS 4.3.1 safely without upgrading baseband. You will also read why it is important to preserve iPhone 4 baseband if you want to unlock your iPhone 4. Ultrasn0w is yet to be updated to support unlocking on iOS 4.3.1 but the untethered jailbreak has already been released. In case you don’t know what your existing firmware version or baseband version [...]