I would think, @Eileen4, that the likeliest scenario with someone who has been a member since 2012, is unreviewed, and has sent an inquiry rather than just Instant Booking is an unpleasant one.
They possibly cannot Instant Book because of previous thumbs down by hosts.
You can ask whether they have used Airbnb before. You can ask why no reviews. If any part of the answer, or non-answer, seems fishy, just decline.
Maybe just decline now anyway. It doesn't look good, but perhaps they signed up in 2012 and are only trying it out now. Perhaps they are wary of Instant Booking and want to establish communication. (Wouldn't that be great!) Perhaps they will be brilliant guests.
Go with your instincts.