Are you considering staying up all night to clean so that a guest can break your first rule, @Kadija4 ? If you want to, sure. But you don't have to.
Guests often ask to check in early. Sometimes they ask, sometimes they just assume. But in any case I say no. It is not possible right now for me to allow it. Like you, I need the time for cleaning, and the time for it to sit between guests.
Say no. Say it nicely, but do say no. Explain to them about the enhanced cleaning if you like, or just say you are afraid it is not possible. Don't mention the staying up all night part. They won't care about that.
Is anything open near you where they might go? An outdoor café or something? You might suggest that to them.
Wishing you the best! Get some sleep! : )