Restore content from iPhone SE backup (on Mac) onto iPhone 5

I tried to restore the content from my broken iPhone SE (64GB, last or at least second to last iOS) onto the older iPhone 5 (28.7GB OS 10.3.4) from the backup on my Mac, which did not work. 

First I was asked to disable the app "Find my iPhone", but after that it still did not work. 

Error message is: 

“iTunes could not restore the iPhone “XYZ” because the backup was not compatible with the iPhone, that is being restored. You must update the iPhone to the latest version of iOS before it can be restored from this backup.

However the iPhone 5 was updated to the iOS version (10.3.4) when being reset and is up to date.

So is probably due to the memory mismatch, even though I used only about half or the memory of the SE, of which again half were pics, that I believe are not backed up.)

Or is there also a problem to restore from last or second to last iOS to 10.3.4 ? 

Any suggestions? 

Might I have the same problem when I buy a refurbished iPhone SE (64Gb) and try the same? 

I could still sync the iPhone 5 with my Mac and retrieve in this way Contacts and Calendar? 

(This is an emergency reactivation of the iPhone 5, which I still have on hand!)