In terms of flexibility of check in time, I'd suggest not to expect what you can get with hotels, eg. late check in time without prior notification.
We didnt get to check in at all.
In the beginning, on that day particular day that we check in, at 9am, the host responded very quickly, accepting our booking. My & my group were very happy.
We then worked our way around the town, keeping our host informed that we would be checking in late, at 9-10pm. At 7pm we still had a good communication.
We then went a bit later that our initial expectiation, and what happened was we failed to inform the host between 7-10/11pm that we would be checking in late, actually later than our previous estimation which was at 9-10pm.
At 11pm, the host asked us to find another place to stay.
We were grateful that we were able to find another place to sleep.
We didnt contact Airbnb help center, we only learnt to detailed terms & conditions only when we have returned to our home country.
That was my personal experience & doesn't necessarily happen to you. Please refer to other reviews for more objective assessment & detailed terms & conditions.
BLessings to all.