@Peter1037 These probably aren't Requests, but rather Inquiries. You only have to write a response - it's not necessary to decline or pre-approve them.
If someone sends a Request, it's binding - the second you hit Accept, they get charged for the dates specified. It would be very odd if someone was willing to risk losing money just to ask a question.
If you do get an inappropriate Request, decline it. The "penalties" are mostly BS scare tactics on Airbnb's part - an arbitrary drop in your Acceptance Rate has no real or lasting consequences, but one bad booking can do immeasurable harm to your home and reputation.