Can I check-in early

Sometimes

You can check in, but they will not allow you into your room early.

You can check in but your room may not be ready. Tbey will notify you when its available.

I don’t know

You can possibly check in but not to your room until they tell you it's ready. I would call and ask to verify

You can ask! In the Disney app you can put a time you’d like to check in, they do their best to accommodate the best they can. I’ve always gotten early check in when I asked on the app.