Can a professor I didn't mention in my application accept me as his M.Sc. student? A professor that I contacted earlier as a prospective student replied to me (and asking for interview) late when I already have submitted my application. I didn't mention him in my application, since I thought he might not be interested and deadline was near and I mentioned other professors who replied to me. If the interview is successful, can he still review my application and admit me under his supervision? 

Note: I can't edit my list of Professors on my application, but I can still edit my SOP (maybe mention him only in SOP?).
The simple answer is: yes.

At many schools it is often the case that professors discuss the applicants outside of the official application system. Other professors may have recommended your application to the professor in question, which is why they are asking for an interview with you now. I suggest you concentrate on doing as well as you can for the interview.

Don't worry about the details of their internal process - you don't have any control over that. If the professor wants to work with you, there is usually a way to make it happen.