File naming conventions in reactJS?

Regarding naming conventions, ReactJS is unopinionated.

There isn't an official guideline or statement about the questions you raised. You won't find them in the documentation either.

It's a personal (team) preference. If you struggle to enforce one, you could stick to something like Airbnb's mostly reasonable approach to React and JSX.

PS: As long as you're consistent, I would say you're safe.

Based on 'Google JavaScript Style Guide'

File names must be all lowercase and may include underscores (_) or dashes (-), but no additional punctuation. Follow the convention that your project uses. Filenames’ extension must be .js.