Replacement iPhone 6 Won't Sync

[typecase]

So I had an iPhone 6 Plus and had the latest iOS 9.35 on it. I could sync my music, back up, etc with iTunes 11.4 running on 10.6.8 without problems until my phone had charging problems and I had it replaced by Applecare yesterday. Yesterday I backed up the old phone and made it sync with iTunes 11.4 on this very computer. Now the new phone (exactly the same as my old one) says that that a newer version of itunes is required even though it was this version that created the backup on my computer only yesterday.

I'm a Snow leopard holdout and use Soundtrack pro which won't work on the new OS. Any ideas?

 

[Gav2k]

Ditch the backup and use iCloud to restore your contacts etc. Then turn iCloud backup on for future restores.

Also check you may have been backing up to iCloud in which case a simple restore on the phone will allow you to restore from that backup

 

[typecase]

Thanks for the suggestion but I can't. My phone has already been erased and the only backup I have is on the computer. It seems I'm being forced to upgrade (which I absolutely hate). I want to upgrade on my terms and when I'm ready.