I have never mounted a sight on a gun so this may be a dumb question, how is it even possible to mount it backwards, it seems like it should be something that only fits one way?
It depends on the gun, the rail and the scope mount.
There are scopes where the front end is larger than the rear as well to confuse the issue.
You can't mount a scope wrong on a stock AK as the rail is on the left side.
You can mount a scope on one backwards in its' mount but it would look real obvious that it was backwards.
If you were familiar with guns and scopes at all, at first glance through a scope you would realize it was backwards.