For those who want to work on the game past NaGaDeMon, is a separate entry on their Itch io library requred, or any sort of distinction? I don't mind keeping a "NaGaDeMon2021 version" entry on my game's download page, if that's what it takes.  I just want to play it safe by asking; so no one comes to my game, tries a much later version, and erroneously thinks, "Wow they got all this done in a month?"

I think it is all aok. No NaGaDeMon police are going to bash down the doors! If you take a lok in the Discord you'll notice a lot of us take games we either manged or just missed out on completing this month and polish them up for a full release at a later date. In fact, I just finished on a Kickstarter for my 2020 NaGaDeMon entry!