SIM from jailbroken/unlocked iPhone 3G to non-jailbroken 2G: Can it be done?

[XyloGal]

I have a jailbroken & unlocked iPhone 3G running 06.15.00 firmware, version 4.2.1 (I have T-Mobile).

My screen is badly broken and also has the notorious "dead spot" that doesn't respond to touch. Rather than repairing my phone, I wanted to try something else first.

I got a nearly-new iPhone 2G from a friend, but it is not jailbroken (friend uses AT&T).

What I want to know is if I can jailbreak the 2G, unlock it, pop in my SIM card and have it work. Is that possible? And if so, what steps do I need to take first?

Thanks!

[i.Annie]

You can unlock the 2G by jailbreaking it and unlocking with bootneuter. You can kill two birds with one stone by using Redsn0w 0.9.4, after upgrading it to 3.1.3 if it isn't already on that fw version already. I suggest that bc it's the latest fw version for that device.