Unlock iPhone 4 on iOS 4.2.1 / 1.59.00 Baseband after Greenpois0n RC5 [How to Guide]

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The below step by step guide will allow you to update your iPhone 4 to iOS 4.2.1 with preserving 1.59.00 baseband, which means that you will be able to unlock your iPhone 4 with ultrasn0w 1.2.

STEP 1: Download TinyUmbrella from here.

STEP 2: Open TinyUmbrella then click on "Start TSS Server"

STEP 3: Open iTunes.

STEP 4: Now, Click on "Restore" NOT "Update"

STEP 5: Now you will get "Error 1013" which means that your baseband has been preserved.

STEP 6: Exit iTunes.

STEP 7: Now you have to jailbreak your iPhone 4 with the Greenpois0n RC5, follow our guide posted here.

STEP 8: Finally you can unlock your iPhone 4 running baseband 1.59.00 using Ultrasn0w 1.2, follow our guide posted here.

Note: this guide is only work with iPhone 4.