Hi BTB, I believe what you are referring to is the requirement for all non Chinese nationals to be registered with the local authorities (I think this is the police but am not sure). From what I remember the requirement is that anyone not staying in a hotel, with a total visit time exceeding 24 or 48 hrs, is required to carry out the reporting process by themselves (otherwise this is done by the hotel).
However, this is just from my memory and I would strong encourage you to check with the relevant authorities for the exact rules and process. Perhaps the Chinese Foreign Ministry office in HK (see link) could help.
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Best luck