Updating iphone 3g to 4
You can obviously easily resync your music but you’ll lose all your i Phone text message backups, contacts, apps, and pretty much anything else that made it your phone.
If you’re totally fed up with i Phone 3G and i OS 4, you can always just downgrade to the prior OS version, but it’s not a particularly fun process and you obviously lose out on all the i OS 4 features.
Disclaimer: Jailbreaking an i OS device is an unauthorized use of Apple's software and may result in security vulnerabilities, instability, and the disruption of Apple services.
Doing so voids Apple's user-end-agreement and Apple reserves the right to deny service to any devices that have used unauthorized modifications or software.
This will make sure you update to the latest i OS version but don’t update the baseband, which is the key part in unlocking your i Phone…
This being said, here is what you have to do to unlock your i Phone 4.1 using Ultra Sn0w. If you are still on i OS 4.0.1 (or even earlier version.ie 3.1.3), then you can use Pwnage Tool to jailbreak your i Phone while preserving the baseband (see our guide here).Technically, it’s not possible to unlock an i Phone that has been updated to i OS 4.1 because there is no unlock available for the i OS 4.1 baseband.Now depending on your situation, there might be a way to unlock your i Phone.