I've upgraded my iPhone 3GS to iOS 5 and hence changed my baseband to 5.16.05. Now it is not possible for me to unlock the phone. Is there any way I could get both GPS and phone working?. I've done jailbreak with redsnow. I don't need iOS 5 and is willing to downgrade without breaking anything. Is it possible to do it?
By now it is possible to down-grade your baseband - at least for the iPhone 3G and 3GS (unfortunately not 4/S) - from the iPad's 06.15 to 05.13.04 (un-lockable) thanks to the great work of the iPhone Dev Team:
The iPhone Dev Team is happy to announce a baseband downgrade option in redsn0w for those who are using the iPad’s 06.15 baseband on the iPhone3G or iPhone3GS.
Typically you’d have the 06.15 baseband if you unlock with ultrasn0w but updated your iPhone baseband past 05.13.04. With this new capability, you can now downgrade specifically from 06.15 to 05.13.04 (even if you never had 05.13.04 on that device before). This gives you the best of both worlds: ultrasn0w compatibility and a normal iPhone baseband with full GPS and the ability to use stock IPSWs again.
See this post on their blog.