I finally made it on an iPhone 3G, 4.2.1, 5.15.04!!! Thanx for the tutorials, although they contain only bits of information, and if you get stuck anywhere you'll have to google further.
To succeed, I used redsn0w v. 0.9.14b2, not the latest one (the latest one will give you faulty baseband after downgrade with no wi-fi, bluetooth or IMEI, and you will have to start all over again).
After upgrading the baseband to 6.15.00, I got stuck on apple logo (bricked phone). To bypass this, you need to download, and Select IPSW iOS 4.1 (not 4.2.1), and use "Just boot" option. After the phone boots, it will be buggy (the screen), but it will become alive again. Check if the baseband is 6.15.00. If yes, proceed to Jailbreak in redsn0w (this time using 4.2.1 IPSW), and tick the boxes Install Cydia, and Downgrade baseband. After it is done, you will have an iPhone with baseband 5.13.04, which you can unlock with ultrasn0w, but (most probably) with "No service" bug. To resolve this, follow the tutorial concerning this matter, and voila!
iPhone unlocked.
This procedure felt like walking through thick bushes...
how to unlock you iPhone just go on your iCloud account on a computer go to finder click devices click the device logged in to your iCloud click listed then put new pass code then got to your iPhone put in new pass code. your phone will ask for iCloud or apple id then put the pass code in that then the iPhone will be unlocked
I can't seem to figure out how to unlock my phone.
I have 3gs with 6.1.6
modern firmware 5.16.08
I have jailbreak with redsn0w
Installed Ultrasn0w
I am stuck on "No service"
Ive tried so many things I cant figure it out.
uninstall ultrasn0w, use redsn0w to downgrade from ipad baseband, that should bring you to baseband 5.13.0 or something like that, then install ultrasn0w again, good luck