@Natasha388 Yes, any person with an active Airbnb account can send you a booking request regardless of your Instant Book settings. The only requisite you can set for requests is "profile photo required," and even that could turn out to be a photo of anything.
There's not a penalty for declining an individual request, but after multiple declines you'll start getting nasty automated threats from Airbnb saying that you could get delisted if your acceptance rate gets too low. They won't reveal what the threshold is, if that even exists - this is mostly a tactic to keep you scared of declining. So when a request is genuinely unsuitable, it's better to decline than to feel threatened into accepting.
That said, I don't feel that having no reviews is in and of itself a good reason to decline a guest - and nor are positive reviews are good reasons to accept. Many, many hosts write disingenuous reviews "nice" reviews even when they had a guest from hell, and plenty more hosts can't be bothered to review even their good guests, so this is not a useful screening method. The best predictor of how the stay will go tends to be the quality of communication, so if a get a request from an unreviewed guest, I suggest having some follow-up questions prepared and decide on a case-by-case basis.
