It’s not a question of “allowing”.
By definition, restoring a full image backup will completely overwrite everything that exists on the hard disk, replacing whatever was there before, no matter what it was.
So, sure, the previous operating system, along with everything else on the hard disk, will be overwritten and replaced with the contents of the image backup.
The real question is: will what you’ve just restored then work?
Most of time, the answer is a very short “no”.
I’ll explain why that is.