Question My protagonist is also the main character. At various points I want to have either the MC or the author be the narrator. I assume that is acceptable.
Also, sometimes one or more of the other characters might also be the narrator, or give his recollections. In the either case, the reader might not even know for sure whose POV is being expressed, and might or might not ever know, except that the POV is clearly neither that of the author nor the MC.
For me, it seems all of this could work very well in a particular story I'm imagining. And, I believe I have seen these representations in other stories here and there.
I think you may be opening up a big can of pitfalls for yourself.
Readers typically imagine themselves in the shoes of the character from whose point of view the story is written. When that point of view becomes unclear, it confuses the reader. They know longer know who they are in the story. It's a bit like an actor breaking character. Suddenly, they are not the person you have been imagining them to be and empathizing with, and the drama is spoiled.
It is possible to have a frame narrator. This is usually a character who then reports what other people say or the contents of other people's letters or journals. The reader understands that each person's story is being conveyed by the frame narrator.
However, if you
have an author (or omniscient) narrator, and also have your main character narrate, how is the reader to understand the relationship between the two? Should the reader understand that the author is relating what the main character says about his story?
It is also possible to have multiple point of view characters. But if the reader does not know who is narrating at any given point, the danger is that you omit any context in which the story can be understood. How can a reader have empathy for a character when that character seems to have no clear identity? And yet, the reason you write from a character's point of view is so that the reader can partake of the personal experience of that character.
You might be able to get away with some ambiguity if you have a way to make it all clear in the end. Readers will give you the benefit of the doubt, sometimes, for a while.
You also have a little more leeway if you are writing literary fiction, and if the exploration of identity is a theme of the book. But your prose had better be quite riveting if it is to make up for the lack of narrative consistency. If you aren't completely brilliant in your execution, your book could easily appear amateurish.
Overall, while there are no absolute rules in creative writing, I think the challenges you face may be greater than the benefits you might get from creating such confusion.