I hate to tell you this, but I'm pretty sure you're going to get referred to the FAQ on those. Both of those questions are addressed in the FAQ - bot original and 'new'.
I'd read those first, then come back here and possibly post a more specific question?
I'm not a Flat Earther, but seriously.... no matter how you slice it you don't have hundres of miles visibility on the clearest of days normally, much less thousands - especially at ground levels. Why would that be any different in a Flat Earth model? There's a start just as an example...
Take care,
John