Unlock 4.0.1 BB 5.15.04 Bootrom 6.04

[whiteTRD]

Hi Guys,
I got an iphone 3gs as a present from my girlfriend. it had 4.2.1 on it but I downgraded to 4.0.1 but didnt realise that the baseband wouldnt downgrade. How can i unlock it? I am not going to go to 6.15 as I don't want to risk any bugs like overheating or failure of GPS.

[Patato22]

You can't downgrade BB that's one
If you don't wanna update to 6.15 well forget about ever unlocking your iPhone for a lont timeeeeee!!!!!!!!!!

[iYeow]

Don't worry about getting the ipad BB, the dev team is working on a solution to downgrade BB.

[whiteTRD]

Ok, so if I upgrade to 6.15, when the downgrade is available, can I restore the phone back to 4.0.1 and what ever baseband? Would this resolve the problems with 6.15 (GPS and overheating)?

Also, what are the chances of the downgrade working for 6.04 bootrom?

Will I be able to restore with an apple ipsw after this? As I have read that if using 6.15 and Ultrasn0w to unlock it, you cannot restore with an original firmware