Restoring backup of previous iPhone 4s (32G) to iPhone 4 (16G)

Hiya,

I've searched and searched but can't find a discussion with this exact problem.

I had my iPhone 4S (32G) stolen recently and obtained an old iPhone 4. I can see my previous iPhone 4S backup (2015) in iTunes preferences but it won't allow me to restore from it to the iPhone 4 (16G) and instead refers to a previous device from 2011 as the only option.

It comes up with this message:

The backup “[iphone 4S]” cannot be restored to this iPhone because the software on the iPhone is too old.

However, it also states my iPhone software is up to date. I have restored factory settings 3 times to no avail.

My previous phone may not have been up to date, does this affect it?

Please help!