Hi!
1. Historical events should be accurate to educate players, but I don't see why you can't fudge things here and there for the sake of narrative pull. You could make a game about the history of an author for example, and portray their fictional works in your game. Or you could make a game about a historical period, like the Roman Empire, and make up your own characters and story as long as it accurately portrays that era. If that makes sense! We can chat further in the Discord if you'd like to brainstorm your ideas there.
2. The theme is pretty open for interpretation, so I'd say yes to any of those examples. Key word here is educational.
3. Discord should be good to go now.
4. I kept the theme pretty open-ended intentionally. Pick a piece of history that interests you and explore it. If you'd like to cover a culture or a festival then do that! It doesn't have to be well-known or lesser-known, that's completely up to you.
Let's chat more in the Discord server!