As most of you know that iOS 4.3.5 only have tethered jailbreak which mean that you have to connect your iPhone 3GS to PC every time you reboot it. When you downgrade 4.3.5 to 4.1 iPhone 3GS you will be able to get untethered jailbreak.
Required downloads to downgrade 4.3.5 to 4.1 iPhone 3GS:
Download Ireb4.
Download - Part 1 - Part 2 - iOS 4.1 custom firmware (made by sn0wbreeze)
Download redsn0w 0.9.6 (mirror)
Download iTunes 10.4
How to downgrade 4.3.5 to 4.1 iPhone 3GS :
Step 1: Run Ireb4 , your iPhone 3GS will enter dfu mode.
Step 2: Go to iTunes and flash 4.1 custom firmware ipsw.
Step 3: Jailbreak your iPhone 3GS with Redsn0w 0.9.6b6 - follow
Step 4: Unlock your iPhone 3GS with ultrasn0w - follow
Here's the step by step guide:
STEP 1: Download redsn0w 0.9.6b5, iOS 4.2.1 for your device(download links at the end).
STEP 2: Update to 4.2.1 firmware using the IPSW file you just downloaded via iTunes 10.1.
STEP 3: Launch Redsn0w 0.9.6b5, and browse for iOS 4.2.1 firmware final version.
STEP 8: This step is only for these devices iPhone 4, 3GS (New Bootrom), iPod touch 4G, 3G, 2G, iPad. While this is tethered jailbreak and whenever you want to do anything related to jailbreak like SSH your device, or running Cydia, you must first run your device in the so called “jailbroken state” on every reboot by using “Just boot tethered right now” option.
Step 4: Unlock your iPhone 3GS with ultrasn0w - follow
Step 1: Open Cydia on your iPhone 4 or 3GS, Go to Manage->Sources
Step 2: Now tap on “Edit”, then tap on “Add”
Enter the following repo ultrasn0w.com then tap on "Add Source" as shown below.
Step 4: Finally, restart your iPhone and you should now enjoy an unlocked iPhone 4 or 3GS on iOS 4.3.2.
