@Melina84 Yes, it is correct that hosts get penalties if they decline requests- it affects their Acceptance rate, and no, a guest doesn't have any penalties attached to withdrawing a request and nothing appears on your profile to indicate that you've withdrawn a request, or even many. If you send an Inquiry, rather than a request (click the Contact Host button under their listing description), the host can pre-approve it so you can book it, or simply answer that the dates aren't available without receiving any penalties, and the Inquiry just expires in 24 hours, so you wouldn't have anything to withdraw.
A host, of course, should have their calendar up-to date and synced with any other platforms they list on, so this sort of thing shouldn't happen- available dates shown should indeed be available. But there have also been a bunch of calendar glitches on Airbnb lately- hosts have been reporting that dates are showing as available to guests when they are in fact blocked on the host's view of their calendar, and dates that are fully available show as blocked on the guest side. So it may, in fact, not be the host's fault. There are many tech glitches on Airbnb, which frustrate hosts no end.
Make sure you read reviews rather than just look for the least expensive places, and places that are new listings may have inexperienced hosts that aren't yet adept at working the platform. If a host has several "Host cancelled this reservation XX days before check-in", you'll probably want to stay away from listings like that, as well.