I didn't change planes in Hong Kong, but flew from Beijing to London and changed planes in Frankfurt. When you transfer, you only need to take your carry-on luggage. The checked baggage airport will be responsible for your transportation. The plane from Hong Kong to London will be checked again when boarding (even if it doesn't leave the airport when connecting). The procedure is the same as usual airport security check (no water, etc. ).

Things sold in duty-free shops in Beijing and Hong Kong will be packed in sealed bags for you (meaning you bought them in duty-free shops). Remember not to open them before leaving London airport. The rest should be fine.

The bathroom in economy class is very narrow, basically only enough for one person to turn around, and the sink is too narrow to hold too many bottles and cans visually. The seat can be tilted backwards, but it can't be put down when it is placed at a maximum of 30 from the vertical direction, so it is uncomfortable to sleep. It is recommended to wear an eye mask and earplugs.

The signature of the entry card should be consistent with the signature on the last page of the passport.