Yes. The night is managed on your phone; backup and share links need a connection.

Not to play. They get invites, recaps and the group ladder as web links. They can install it to claim their seat and follow their own stats.

No. It only tells you who owes whom, with the fewest transfers. You settle however you like.

Subscriptions are managed by Apple: Settings → your name → Subscriptions on your iPhone.

In the app: Settings → Account → Delete account. This removes your account and everything backed up to it.

Coming later. iPhone first.