@Noreen28 Anyone can send an Inquiry. If they are trying to get a discount, they wouldn't Instant Book, they would send an Inquiry.
Yes, email addresses and phone numbers are hidden until a booking is confirmed. Guests wanting to communicate off-platform is usually because they want to try to make a private deal, avoiding Airbnb fees. Why would you want to waste time sending information to a guest who is just inquiring via email? Just send them a return message saying you don't discount and be done with it. They probably sent out inquiries to 15 different hosts.
If your listing description is complete and your photos are clear, there's no reason a guest needs more information that can't be conveyed through inquiry messages.