Need to downgrade your iPhone for a 1.1.2 jailbreak or SIM unlock Here is a simple how to

1.Enter DFU mode: power + home for 10 seconds, then home for another 10 seconds. The phone will remain completely back. If not, repeat. iNdependence will also do this step.

2.Select the desired firmware you’re downgrading to; those can be obtained below.

3.In iTunes hold Option/ALT (on a Mac) or Shift (on Windows) and click “Restore.” Select the ipsw you downloaded.

4.At the end of the process you will receive an error; this is normal.

5.Get IPHUC below and issue the following commands:
cmd setenv auto-boot true
cmd saveenv
cmd fsboot

Congratulations — you just downgraded!


source: iphone-elite