stevensonleehk, welcome to our little pond on FT!
Finnair has said some routes have a "full-flat-guarantee", a guarantee that is more of an ambition - there have been no reports of any compensation when / if guarantee fails.
HKG is not on that list.
Or more exactly, it is said to be on the list during winter season. No dates have been published though. And with the A350s entering the fleet this autumn and A340s leaving when schedule allows it, this future is especially difficult to tell.
In September, AY62 still operates Mon and Fri and is (so far) scheduled as A333, ie full flat new C.
AY70 is scheduled as A340 until 18 oct, where 3 out of 7 planes are old C.