When booking, you pay a deposit of one nights room rate plus tax. No change or cancellation fee will be charged if you make your modification more than 5 days before arrival. 
You can book up to three rooms per adult Annual Pass. 
You can book with a valid Annual Pass, an exchange voucher or with the intent to purchase an Annual Pass, as long as you present a valid Annual Pass or exchange voucher upon check-in. 
Thanks to Small World Vacations for info.