How did people begin their lives when a new version of the Matrix started?

As in, did they just kind of pop into existence inside of The Matrix once a new version started? Assuming they had artificial memories uploaded to their consciousness by the machines.

Also, how does time progress? And human history? The sixth version is modeled around the year 1999, so I wonder how long is it actually 1999? Does it ever go past that? Did that version start at some point in time before that?

Another question is how do people within the Matrix procreate? If two people decided to reproduce, would the machines then create another human to hookup and sync with those peoples’ version of The Matrix?

These are the questions I start asking as I’m falling asleep and about to go to bed.