Question 1: Have you ever actually started a level 1 PC and got, through gaming (no-level skipping) to level 20?
A friend & player in my 4e Loudwater game played Lirael the Ranger from level 1 to level 29, while also writing a bunch of good-selling teen fantasy books, creating fantastic hand-crafted magic wands, doing a professional paint job on several of my minis, and raising a son &
husband - not everyone has the dedication to put 5.5 years into the same PC though, or
the skill to keep them alive through 5 and a half years of my GMing.
I have another friend & player has played Hakeem the 5e Barbarian from 1 to 19 over the past 2.5 years, but he's planning to retire and become a house husband just as soon as he faces & survives his final battle with Kainos the Warbringer, demigod son of Ares (any day now). We'll see how that goes...
My son played William the Wizard MU 4 to 17 in Classic before he died, and has played William's son Bravery from Fighter 1 to 19 now. And BiTD I had players with god-level 1e AD&D PCs.