1: No spam or advertising. This basically means no linking to your own content on blogs, YouTube, Twitch, etc.
2: No bigotry or gatekeeping. This should be obvious, but neither of those things will be tolerated. This goes for linked content too; if the site has some heavy "anti-woke" energy, you probably shouldn't be posting it here.
3: No untagged game spoilers. If the game was recently released or not released at all yet, use the Spoiler tag (the little ⚠️ button) in the body text, and avoid typing spoilers in the title. It should also be avoided to openly talk about major story spoilers, even in old games.
No, GameMaker Studio. That engine had it's own controversy over moving to a subscription model, but nothing as egregious as Unity.
That's a shame. I remember messing around with GameMaker back in the day. It was a great way for a total beginner to make something playable.