Is it okay not to stay overnight in Hong Kong? For example, where can I go to spend the night? Will the police ask?

Yes, if you go out to play and do legal things, the police generally won’t ask. If you wander aimlessly or harass others, the police may charge you with loitering or disorderly conduct in a public place. Some independent travelers in the mainland will go to the 24-hour McDonald's to rest, but the police will not care. If you walk backwards, become nervous, or do some strange behavior when you see the police, the police may think you are suspicious and will question you