How can I iPhone restore in iTunes without upgrading iOS? I am trying to restore a set of my iPhone5C backups I made in iTunes to my iPhone4S. My iPhone4S is still running on iOS 7.0.4. I don't want to upgrade it because iOS8 on iPhone4S will almost be unusable (the current iOS7 is bad enough on iPhone4S).

I have tried doing this directly in iTunes using its restore function, but when I do so, iTunes forces me to update my iOS to 8.3. If I refuse to upgrade, the restore function will abort and I cannot continue with my restore from there. 

How can I perform the restore in iTunes without having to upgrade my iOS?
You can't.

Restoring from another device's backup will update to the latest iOS the restored device can use.

The only way would be to restore from a backup initially made from that same device, using that iOS.