All of mankind is either gathered at the start of the 1,000 year reign and that group is static in number as they are not given in marriage so no children are born to them in that period of not in the New Earth verses because they reside inside the walls of New Jerusalem in the new earth. As big as the city is they would overfill it eventually so they remain at a constant population. They are the first to be allowed through the gate that requires an interview with each individual before they enter the 1,000 year reign.
Everybody not alive at that time is resurrected to life at the GWT event so they are the last of mankind to be given immortality and a sinless heart. The angels will be in their new heaven so immortal men are free to explore the universe as that is the new earth. As God of the living and being a perfectionist I do not see any other options for what the various passages mean in real terms. If not for some prophecy Jesus could convert everyone as easily as he gathered Saul.
Don't be shy about hammering me with questions as I make some posts shorter than they should be.
Sorry mate but now I'm more confused as ever.
What on earth is the interview? Why does it only apply to the first?
To be honest I have not researched thoroughly end time eschatology, rapture, pre-post, millennial, pre-post.
I just focus on the here and now.
There is nothing I can add to that.