Hi @An10
Have you had a look at the Airbnb help centre and searched the forums here?
Lots of useful information including how payments work.
1. You normally need to accept a nominal tiny amount so Airbnb know they have the right account. I don't use paypal, but there might be some information about this under the help centre
2. Have a look at long term bookings on the help section. I believe you get paid monthly. You can set a deposit - see the Help Centre. You can't charge one. Airbnb holds it against a guests payment system
3. If you have a booking confirmation then you have an accepted booking. If you have Instant Book turned on, you will probably want to turn it off so you can vet each guest before accepting a booking.