2) Multiple Rates - if you want to send multiple prices for a room you must have a rate id for each rate in Booking.com and a matching rate with the price and rate id setup in Beds24. See the Beds24 section above for more details.
3) There are two ways to stop selling a room when available inventory becomes zero. A zero for availability is the normal way to stop selling, this means if there is a cancellation of an existing booking the room will immediately become re-available for booking at Booking.com. The alternative is to close the room, this means the room will not be automatically re-opened after a cancellation. The room will only be re-opened after the next inventory update from Beds24. This can reduce the chance of double further over bookings if the room is already over booked but means the room will be unavailable for re-booking for a short period.
4) Single occupancy prices must be activated within booking.com if you are sending them.