Thanks for the thorough reply :D
I do think some of these things could have been communicated a bit more clearly. I get that discovering everything for yourself is half the fun, but when it's possible to make progress without properly understanding the mechanics you are using fully, you risk having the player get very frustrated later on in the game.
I tried approaching this game very algorithmically (as in, making up rules for myself to follow in order to minimize casualties during expeditions) after screwing around a bit to figure out the core gameplay loop. It's how I usually play puzzle games, and I find the fun in "refining" my "algorithm" if I discover it to be inefficient or ineffective. I can't really do that if I don't understand the way MY abilities work. Although it could just be a "me" thing.
I absolutely adore the idea of hiding the choice to stay in heaven without going through hell behind the innocuous "escape" button. Extremely clever all around.
One last lore question: what actually happens if you "choose" ending 3? Does the entity release you from the void (if so, it'd be cool to instead have a 1 time exit from the void so that you can get a chance at redemption or even be re-tempted to return to the void and explore it further)? Does it kill you permanently? Or are you still stuck in the void and the choice you're given is simply whether you LITERALLY "accept your fate" (if so, maybe you can make quitting in the void a secret ending as well).
Fun fact, by the way: in Christian theology Hell is considered less of a place and more of the state of a soul being eternally separated from God in every meaningful sense: the suffering comes from the permanent severance of the union between creation and Creator. The fact that the void is the only way to actually permanently deprive you of heaven (since hell is escapable, even if you enter early through the password room) makes it more of a "biblical Hell" than the in-game hell itself, ironically. It's also thematically appropriate: you disobey "god", he puts you in "hell" (which I guess here would be more akin to the Catholic Purgatory, as it's very painful but also temporary), you escape, "god" gives you a crash course on why what you did was bad and gives you one last choice to either redeem yourself or damn yourself forever through the password room (in fact, he actively tries to nudge you towards ending 2 with the "Do you remember what Heaven looks like" hint. He absolutely never mentions anything about a third option for the password room: you discover it by "sinning" the way you always do, by searching for secrets in "Memories of the end 10").
Absolutely lovely game all around. It scratched this very specific itch I have for games hidden within games that recontextualize everything. Your "Idle Nightmare 1" was excellent in the same way, with the entire journey through the darkness always quietly being an option during your first playthrough, only to recontextualize everything during the second. It was the reason why I was actually quite disappointed when I tried out its sequel: the "surface layer" that used to itself be an entire pretty fun game on its own in the the first game was extremely flimsy in the second, almost immediately giving way to the forest stuff. That, and I simply didn't find the shock humor and the adult stuff particularly appealing.
Anyways, on "Mapped by our ancestors", it's a solid 4/5 for me, though I'll rate 5/5 because of your thorough reply. Your games are absolutely fascinating, so keep being creative :)