Do hotel events require registration by the organizer?

No need. Because holding an event in a hotel is not in an open-air public place, as long as it is not in an open-air public place, the organizer does not need to register. Only in open-air public places, registration is required, and the route, number of people, etc. need to be recorded. Reporting requirements are very high, so hotel events do not require the organizer to register.