Jay Freeman (Saurik), the developer behind the infamous Cydia store for iPhone has found a way to downgrade iPhone 3GS from firmware 3.1 to firmware 3.0. This process will only work for those who have saved their SHSH to Cydia Server, for more on SHSH, read the complete detail blog post by Saurik here. Also to note here is that while this method will help you downgrade your firmware from 3.1 to 3.0, your baseband will not be downgraded which means you cant unlock it for now.
The following step by step guide will help you downgrade your iPhone with firmware 3.1 to firmware 3.0.1. For those of you who upgraded to iPhone 3.1 may have found your device to be locked and un-jailbreakable as the tools for jailbreaking and unlocking are not out yet for iPhone OS 3.1. Fortunately, there is still a way to downgrade your phone from firmware 3.1 to 3.0.1. I have tried it on my iPhone 3G and it works perfectly on it.
Apple is expected to announce the new iPhone OS 3.1 firmware at their “It’s only rock and roll, but we like it” event this Wednesday. All iPhone users who have either jailbroken or unlocked their iPhone with firmware 3.0.x should avoid updating to iPhone OS 3.1 unless the infamous Dev-Team releases updated versions of redsn0w and ultrasn0w for firmware 3.1.
iPhone OS 3.0.1 has been released to fix SMS exploit which could remotely control the victim’s iPhone. This guide will help you update to the latest iPhone firmware 3.0.1 while keeping your jailbreak and unlock intact. This guide applies to all the iPhone’s – iPhone 2G, iPhone 3G and iPhone 3GS.