restore iphone4s backup onto old iphone3gs

[slickbomb8]

hello,

a couple of months ago i used to have an iphone 3gs and switched to the iphone 4s. I used the same personal computer itunes to maintain both phones. when i got the iphone 4s, i was able to restore my latest iphone 3gs backup onto it successfully.

When i go to Preferences -> Devices, i see a 3gs backup timestamped several months ago when i switched to the 4s. I also see my latest 4s backup timestamped last week. Sadly, my 4s is now broken so i want to reuse my 3gs. My plan was to use the latest 4s backup and restore that to my old 3gs phone.

The problem is, when my 3gs is connected to iTunes and I choose to "Restore from Backup", the only choice i am given is to restore using a backup of my old 3gs before i switched to the 4s, timestamped several months ago. I expected to see my latest 4s backup from last week as a possible restore point.

Is it not possible to put a 4s backup onto a 3gs?

Appreciate the input.

[slickbomb8]

RESOLVED

i had to update to the latest iOS on my 3gs and then my 4s backup was available as restore option.