When I am hosting I usually try to block the night before and after a reservation to allow for cleaning and preparation. So I often allow check in earlier than our 3 pm check in time and allow late check out. I usually wait to offer this to my guests a few days before their arrival, when I can better predict my personal and the Airbnb schedule. However sometimes I do have back to back reservations and then cleaning and prep has to be done between check out at no later than 11am of one guest and check in at 3pm or later of the next guest.
If you want for sure to have the early check in and late check out available to you, you could offer to book the night before and/or the night after your stay. It is easy to extend your reservation to include these nights if they are not yet booked.
Some hosts won't be able to check you in early even if you reserved and paid for the night before since they are not able to be at home until after 3 pm. Other hosts have self check-in or a flexible personal schedule and as long as you have reserved and paid for the night before you can arrive the next morning whenever you wish. The important thing is to offer to compensate the host for extra services or extra time in the space, and to be prepared to make other plans if they say it is not possible.