Hi @Yogita3,
to very good lorna suggestions I would like to add more.
Technically there are no difference from Airbnb to Hotels: in some countries there are hotels in Airbnb and anyway the hosts can offer a lot of services like and more than hotels. And they do: you can book on Airbnb apartments with daily cleanings, breakfasts and more services as rental bycicles, baby sitter, laundry etc.
The check-out at 12 pm is quite normal all over the world. Usually it is about from 10 am to 12 pm but of course there are not strict rules: a host (such as a hotel) could choose a very early check-out to allow for morning check-in which is very appreciate. I'm sure a lot of apartments in Airbnb are flexible, so it can be normal for some guests to expect flexibility even if they have been using Airbnb for years.
Regarding the baggage help, I think it is normal to offer it. As far as possible: if you are a young and weak man or woman you cannot move heavy luggage but offer yourself for the light ones and to carry the heavy ones together. I don't suggest you sit still and watch your guests as they carry all their luggage home. I'm sure you already do.
I would not concentrate too much on customs and traditions, everyone has their own. I would try to be as polite as possible (for me helping with luggage is politness, not only normal) and to make an announcement as clear as possible, as if all your guests were from Mars, giving additional information that you consider important in communications with them. For example if you only offer cleaning on a specific day or the check-out time is not negotiable, say that clearly immediately after booking and in the ad. Please note that flexibility is what many guests expect most, not only about check-out: so try to organize yourself to offer it a little. And try to be "smart" (=professional) in all your communications, study them well. For example it seems to me that you accepted a check-in at 11 am (very unusual time) because she had canceled the reservation. Not many words: "I'm sorry, the late check-out is no longer possible because you canceled the reservation and I took other commitments, otherwise I would have been happy to satisfy you". Even if for your current organization you couldn't.
Good luck!