Thanks

Trust-based. You can do that with on-chain transactions, too. These, too are trust based. In both cases, if the sender decides to undo the payment, he can if he manages to get internet first.

It's basically sending someone the information need to claim funds from the mint. Since both the sender and reciever will have this information, they both can attempt to claim it once Internet is available.

Likely not used in this case, but just fwiw: Briar chat messenger can work over local WiFi or Bluetooth. And so you can use it to chat with folks on airplane without internet...