OS 4.0 Jailbreak & Unlock iPhone 3Gs old bootroom GUIDE (from OS 3.1.3 - 05.12.01 modem firmware)

If you previously accidentally update your iPhone 3Gs to OS 3.1.3 and updated your modem firmware to 05.12.01 you can now jailbreak and unlock with new OS 4.0 but with the condition your iPhone 3Gs is OLD BOOTROOM! All credit go to Dev-Team . Sorry but this guide is for mac user only!

OLD BOOTROOM - Check your model number....if it begins with "MC" then you have the new bootrom if it is not "MC" then you have an older bootrom also check the 4th and 5th number in you serial number if it is lower then 40 then you have an old bootrom.

First Step - Download all the require file
iPhone OS 3.1.2 - Download from here
iPhone OS 4.0 - Download from here
redsnow mac 0.9.2 - Download from here

PwnageTool 4.01 - Download from http://blog.iphone-dev.org/

2nd Step - Plug in your iPhone 3Gs to your mac and open up your itunes. From itunes, option click restore and choose OS 3.1.2 that you just download. Don't get panic when you get an error message. It is normal to get the error message. Restore with OS 3.1.2 TWO TIMES.

3rd Step - after you have restore your iPhone 3Gs two times with OS 3.1.2 you will still be in the recovery mode. Open up redsnow 0.9.2 and follow the steps in the application. Remember you will use OS 3.1.2 together with redsnow and please do not install Cydia. Refer to the picture below and uncheck everything.

4th Step - Once you done with redsnow, you will now successful jailbreak with OS 3.1.2 but without the Cydia. You will then create a custom ipsw with the pwnagetool 4.01 with OS 4.0. When you done option click restore again but this time you restore it with the custom ipsw (OS 4.0) that you created with pwnagetool 4.01 (Please do no restore with original OS 4.0! you will lose your jailbreak + unlock probably forever)

5th Step - When you finish restore with the custom OS 4.0, you iPhone 3Gs now is successfully jailbreak with OS4.0. The only thing you need is to unlock it so that you can use any other service provider other than the one locked to. To do the unlock, open up your Cydia. It will probably update your Cydia for sometimes. When it is done updating your Cydia, tap on 'manage' and then tap on 'Sources'. Touch “Edit” and then “Add”. You will be prompted to enter a URL for repository source. Enter “http://repo666.ultrasn0w.com” and finally “Add The Source”. Leave the rest for Cydia as it will update the sources.

6th Step - When it is done, go to 'search' and search for ultrasnow and install it. Once it is done installing it will prompt you to reboot. Please do so and you are happy to go with any carrier. Congratulation, now you have a jailbreak+unlocked iPhone 3Gs with OS4.0

Any Question please leave a comment and I will reply you as soon as possible.