Is circular reasoning, or another fallacy?

This is a nonsensical statement. Its unintelligible and it makes no real point. It has no conclusion and premises so its not even an argument. For it to have a circular reasoning or other fallacy it would first need to be argument which it is not.

You run into this sort of "thinking" frequently in all sort of human justification of things. Religion is just one of the more infamous uses of circular reasoning. It also occurs in philosophy and you have to be on the look out for it.

"Circular reasoning doesn't accept any other interpretation other than its own because it doesn't allow any other interpretation. So if an argument doesn't allow another interpretation it is circular reasoning." is also circular reasoning.

Yes, this is circular reasoning. It is also called "begging the question", since the premises and the conclusion follow from each other.

It sounds circular because it's a tight, closed loop. It's similar to using the term to describe the term. For example: Fire is hot; it's hot because it's fire.