I don’t know what engine you’re talking about so I’m going to presume you mean pygame. I personally do not use pygame but I hope this tutorial will help you!
As long as it can be played on web, you can use that engine. You can submit a Windows build but that’s only recommended if the web build is unplayable/unavailable for some reason but it will impact your ratings since not everyone will be able to play it.
No, since games with Roblox Studio are stuck on Roblox, only playable by going to https://roblox.com/games/[id] and downloading the Roblox client, then only then, can you play it. It can’t be exported and published to itch.
(If you are looking for a no-code engine/engine with templates, I recommend GDevelop).
