I'd like to know as well. I'm selling my iPhone Edge to buy the 3G. If I buy a brand new one, it's gonna have 2.30 firmware. Is this reversible and go back to FW 2.80?
Guys. You CANNOT downgrade the baseband (without taking the chip out at least, which can brick your iPhone). You CAN downgrade the firmware, but that is it.
If you get a new phone on the latest firmware (2.2.1), it will have the latest baseband. Meaning you can't software unlock. But most phones are being sold on 2.1 and 2.2.
If you're not on 2.2.1 yet, but you want to be and still have the option to unlock, use PwnageTool to make a custom firmware to update the firmware, but not the baseband. Enabling the soft unlock known as yellowsn0w
If anyone's on windows and they cannot get acess to a Mac to use PwnageTool, I have a custom IPWS on 2.2.1, but still with the 02.28.00 they can have. PM me if you want it. All you have to do if hold shift, then click 'Restore' in iTunes, and choose my custom firmware. This'll upgrade to 2.2.1, it wont update the baseband, and it will also install Cydia.
Oh, if you're on the old 'Edge' iPhone you can unlock on all the new firmwares
