@Elen4570 No, it doesn't have anything to do with cancellations. You can prepprove it if you feel okay about the guest. Then she can go on to book. If she doesn't do so within 24 hours, it will just expire, without any penalties to you whatsover. If a booking request comes in in the meantime, and you accept it, that will take precedence over the Inquiry.
On an Inquiry, you have 3 choices- pre-approve, decline or just message back.
Be aware that lots of Inquiries are just that- people asking questions. they may have sent out inquiries to 5 different hosts. You may very likely never hear back from inquiries again.