How to Unlock iPhone 4 3GS 4.3.3 with Ultrasn0w 1.2.3 [Tutorial]

iPhone dev-team has pushed ultrasn0w 1.2.3 to unlock iPhone 4 and iPhone 3GS running iOS 4.3.3 on old basebands. check out all compatible basebands with ultrasn0w 1.2.3 after the jump

Compatible basebands:

• 01.59.00
• 04.26.08
• 05.11.07
• 05.12.01 
• 05.13.04
• 06.15.00

Incompatible basebands :

• 02.10.04
• 03.10.01
• 04.10.01
• 05.14.02
• 05.15.04
• 05.16.02

iPhone 3GS users:

You have to jailbreak your iPhone on 6.15.00 basebands on iOS 4.1 / 4.2.1, you can follow this guide for PwnageTool Mac or this guide for Redsn0w Windows / Mac (You may lose your GPS)

Requirement: 

You have to jailbreak your iPhone 4 or iPhone 3GS on the latest iOS 4.3.3, you can follow  This Guide (Untethered PwnageTool 4.3.3 for Mac) or This Guide (Untethered Sn0wbreeze 2.7 for Windows)

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 http://repo666.ultrasn0w.com then tap on "Add Source" as shown below.

Step 3: Now search for ultrasn0w 1.2.3 then install it. By installing ultrasn0w 1.2.3, your device became unlocked

Step 4: Finally, restart your iPhone and  you should now enjoy an unlocked iPhone 4 or 3GS on  iOS 4.3.3.