@Dora149 It sounds like you are unclear on the difference between an Inquiry and a Booking Request. (You should have been able to message the host an Inquiry with any dates whether or not the dates are available. If the listing is active and viewable on the site, the listing isn't off the market).
If you receive a guest Inquiry, and they are asking for things like bringing children, which you don't accept, you can just message them back within 24 hours, without clicking on Decline. A simple return message without pre-approving or declining will not be counted against you, as declines are, so never decline an Inquiry. You can safely ignore the messages from Airbnb prodding you to pre-approve.
A Booking Request is different- you do have to either Accept or Decline within 24 hours. But you can still message the guest before that time is up telling them why you can't accommodate their request and asking them to please withdraw the request so they don't get chraged for it, then have to cancel, and wait for a refund.
In other words, there are several ways you can avoid having to decline either an Inquiry or a Request.