Confused Canadian

Re. connection:
(assuming it's the same ticket)
a) if the airline sold you this itinerary they must be pretty confident of your making your next flight - HKG is very efficient (though taxiing times have been prolonged recently)
b) even if some transit corridors are closed at such late hours, transiting through HKG is pretty much a breeze
c) if your connection becomes tight they'll arrange for a ground staff to take you through procedures - not sure what they call 'tight' though
d) if you miss your connection they'll surely offer an alternative flight /accommodate you until the next available flight

Re. Cabin baggage:
IMO they're pretty accommodating w.r.t cabin baggage - as long as you don't bring your kitchen sink
would not recommend overly stretching the rules though out of courtesy for other pax

Enjoy your flight experience