If your check in time is 5 pm, what is the problem? There is no obligation for guests to tell you their plans. Perhaps the person is en route, off-the-grid or is aware that he/she cannot check in until after 5 pm and is ok with it.
This idea that guests are *required* to tell hosts their plans is something that keeps recurring on this board. Keep in mind that getting that information is atypical. Guests are used to arriving anytime after check-in time and expecting their accommodation to be ready. In my 46 years, I have NEVER been asked or volunteered my arrival time or plans. Often if I was asked, the answer would be "I don't know" because I truly do not know what I am going to be doing, if I am going to get lost, my flight delayed, etc.
Of course, it is your home, you can either be there at 5 pm or you can cancel the booking. There are several instances of hosts canceling on non-responsive guests on the day before posted on this board. There is even one on this board where the host was able to convince AirBnB to cancel for them, so the guest got inconvenienced and the host got no penalty.
ETA: I missed your second question. If the guest does not cancel and does not show up, you still get paid everything except the cleaning fee (which is returned to the guest). If the guest cancels you will be paid based on your cancellation policy Also if the guest does not stay they cannot leave a review.