Shanghai to Hong Kong (a few days each)

I am planning a 2 week tour in Japan, and then go via Shanghai for 2 days and then to Kong Kong to fly back to London, as i will be travelling by sleeper train from Shanghai to Kong Hong and staying there for 3 days before my flight back to the UK will i be able to use the 72 or 144 hour exempt visa as i plan on doing some site seeing in both cities? FYI this is for mid 2021 as i am aware this is currently suspended due to Covid.
thanks