These are all larvae of various Lymantriidae species
The one photographed by Sze might be a third instar Orgia postica - not confident on this though.
The photo in BWA's quoted post is of a Dasychira species, but don't know which - it might be a second or third instar Dasychira chekiangensis
Sammy's photo is of an Arctornis species. Again I don't know which and there are at least 12 species in the genus in HK - none properly worked yet.
Swing's photo is also a Dasychira species. It isn't D. chekiangensis, which lacks the white marks.