As opposed to us simply being some other civilization on one of the other billions of habitable planets in that same "first" universe?
So with no other knowledge, it's slightly more likely that we are the first civilization than the 5 millionth.
Of course it's tricky to talk about the "first" civilization in the face of relativistic time, but I'm assuming that there is some way to have an ordering of all civilizations.
You can't meaningfully speculate about the nature of what (if anything) is dimensionally/physically/extra-universally "outside" of our universe.
We don't even know what that means, much less if it exists or what the number/nature of it would be.
Our universe may be a piece of candy floating on a chocolate river in another universe that flows eternally.
It's all just make believe. Make believe can be fun, but let's not pretend that we're doing anything more substantial than what three year olds do when talking about space robots.
Yes, but if we are in a simulation we can almost answer the Fine-tuned Universe Paradox too, two birds with one stone. That is nice for Occam's rasor reasons.