No, not the universe. Some physicists believe they have a pretty good idea of what the universe is and where it came from.
Reality. The existence of the universe requires at least one thing: Existence.
Not time or space but pure, meaningless existence. This is a paradox.
You are right, of course. However thats not a paradox just something beyond our grasp.
Our universe is the only amount of reality we know, there might be more, that universe is expanding "into" existence a room of existence if you will.
why that room is there or how is a question but not a paradox.
the universe could also turn non existing space, negative reality if you will into positive while expanding, during that process
point is yeah, we dont know but I dont see the paradox. A paradox implies that assumption A and B are both right but cancel each other out. like the drake equation
I mean our definitions of reality and existence are getting kinda muddy because we are wandering into philosophy since we are not that far in science.