greetings from turkey...

i have a question about backup of the iphone...

is it possible to recover the "3gs" with the backup of the "2g"?? i am trying but it keeps giving error of sync...

thank you very much for your interests

Yep, it is possible. For example, I had a 2G iPhone. When the 3G came out, I plugged the 3G in to my PC and just told it to restore from backup. When the 3GS came out, I did the same thing.

That said, it's usually better to just wipe the device -- especially when you are dealing with a hardware update. You can see serious battery performance issues and other weird eccentricities if you're using upgrade information based on older model hardware.

What errors are you receiving during the sync? Having that info will help a bunch.