Problem With iPhone 3g on 3.1.2 6.15 Baseband

[ttareen]

I was able to successfully downgrade from 4.1.2 to 3.1.2 and everything was smooth until i tried adding the app colosseum heroes onto it. Colosseum heroes requires 4.0 or higher os, so i decided to upgrade back to 4.1.2, but no luck as of now. Tried using itunes and redsn0w, but both get stuck at the recovery sign. Tried use ireb to kick phone out of it but as soon as it reboots, it goes right back to it. So after all this, i just put the phone back at 3.1.2 and jailbroke it. Now my question is actually 2 of them:

1. Is there a way to upgrade to 4.1.2 with my current situation? Like i have 6.15 baseband on it, can i upgrade to 4.1.2 with it?

2. My cydia keeps crashing on 3.1.2, i open it, and it says loading data, but then just crashes. People say use ssh and stuff but i cant even get to that section of cydia to install it. Any ideas on this?

[i.Annie]

If you have the iPad bb, you should be using a custom firmware to update to 4.2.1. Create the cFW then set into pwned DFU mode, then restore to the cFW. This should not yield any errors.