I believe that this is allowed, I've seen many apps do that already. However, I'm very sure that your home screen needs to be empty and only show stuff like system apps and not any other apps. Once again, I am not entirely sure, but that's how I saw other apps do it. Hope I was able to help!

Face Sharing and FaceTime are a completely different thing. Please contact Apple Support for more help.

They also mention that your playground will be judged offline, meaning that WiFi will not be enabled. As a reminder, here‘s what they say: „Submissions will be judged offline. Your Swift playground should not rely on a network connection and any resources used in your Swift playground should be included locally in your ZIP file.“ Sorry to disappoint you.

All of them are accepted! You can submit both an Xcode Playground or a Swift Playground for Mac or iPad. Just remember that you are not allowed to submit an app, you can only submit a Playground as of this year.

I don‘t think it‘s your code that is the issue. I‘m facing the exact same problem here, and I think that is rather a thing that Apple has to fix. There is a reason why below the toggle it warns you that you may experience lag. On my playground, I have just put in a reminder that tells you to Disable Results before running.