There is a good explanation of what happens when you enter a Black hole in section 6 (p1721) of this very good recent article by David Mumford. General relativity is the theory that describes what happens. You can ignore the equations and hopefully get a better understanding of the issues behind your questions. https://www.ams.org/journals/notices/202110/rnoti-p1715.pdf
That is an interesting theory about the mother universe creating baby universes through black holes. Very interesting information that raises some interesting philosophical implications as to the nature of causality in regards to the source of universes, or the first universe that created all these others.
You might want to look for articles by Ethan Siegal, who writes very approachable (if not entirely accurate) articles for the layperson about physics and cosmology. This won’t give you any ultimate answers, of course, but may help you understand the scientific questions being considered.
Thank you I’ll take a look at his articles. I do enjoy reading the work of experts that can make complex abstract knowledge more easily accessible, even if it it sacrifices some immaterial accuracy for purposes of clarity and communication. However, I do like to think of myself as at least an intermediate when it comes to the fields of physics and cosmology.