Good questions with no real answers, but lots of guesses.
What is in the center of a black hole is not really known. We see neutron stars that are not quite massive enough to become black holes. And we postulate that in the center of neutron stars, the neutrons have broken down into a soup of quarks and gluons instead of being bound into discrete neutrons. But, that is as dense as (we think) we know about.
When the material is compressed further inside a black hole, speculation ranges from it getting crushed down into an even more dense but finite form, or getting crushed into a "singularity" with no dimension at all, or maybe a Plank-sized volume in which we claim there is not further knowledge of the state of whatever is in it.
So, the interesting part of your question to me is what happens to gravity when the matter is crushed? Can gravitational force disappear if the matter all becomes energy? Or, is the energy still as massive as needed to continue the blackness of the black hole?
If gravity disappeared all of a sudden, in some sort of final collapse of matter into pure energy, then would a black hole suddenly explode (i.e., "inflate")? Would that inflation stop suddenly if the energy form "cooled" enough for matter to recondense and recreate gravity?
That is one way that a "bouncing universe" could occur, and it would probably reset entropy in the process.
However, we do see supermassive black holes that are already billions of times the mass of the Sun. So, is that not enough matter to trigger those effects?
Or, do we not understand "space" well enough to know what it would look like from the outside if something like that happened on the inside? Could it already be happening inside black holes we can see, but we just can't tell from "out here".
If it is already happening in some supermassive black holes we have already detected, we know that there is still matter from "our universe" that is going into those black holes, so what would that mean for "their universe" on the inside?
Would it look to them like the Cosmic Microwave Background" looks to us? Would it seem to have an effect on continued expansion like we think "dark energy" is creating for us?
And, for that matter, are we actually already in a universe that is really just like one of those universes?
I can think of the questions, but I don't have the answers.
And the important thing to realize is: neither does anybody else. So, when somebody posts that, something is the answer, rather than to consider that something might be the answer, they are claiming that their own beliefs are fact, and that is not proper science. Which is one of my few per peeves.