How can I restore a 3G with a 3GS backup

[hrus013]

So i convinced my dad to trade his 3GS for my 3G as he doesn't use it for anything but calling, one problem...i cant restore his backup onto my older model phone. Had no issues with putting my backup onto his but when trying to put his on mine itunes wouldn't, saying that the firmware was to old (on the 3G) and needed to be updated before restoring with this backup!

Is there anyway i could get this to work without jailbreaking either iPhone

Thanks!

[iYeow]

Itunes will not allow you to do a backup restore after a downgrade of IOS.
Before the restore, you could use a third party software to backup the infos, after the restore, jailbreak it and then use the third party software to restore the infos.

[hrus013]

I know it is possible with jailbreaking, is there way to do it without jailbreaking though?

[iYeow]

No jailbreaking means no root system access = No third party software backup, so the answer is NO