Sedna,
To sum it up. No.
There are 2 ways to join CX these days. Cadet SO, with no housing allowance, and probably soon by direct entry FO on a base or the freighter, so you will not receive any housing assistance there. You cannot join DEFO in HKG, except maybe on the freighter if you are mad, and even then there is no housing allowance.
PS. B772 is not a rating. B777 rating covers all models.