Ok - I get it now. You intentionally added extra transit time at HKG to travel on the 77W and now - given that it is no longer a B77W - there is no reason to hang around @ HKG and you which to take the earlier flight to TPE. Your inquiry makes more sense now.

I guess all you will get from the this board is to go ahead and try to request the earlier flight. Whether it will be allowed or not is likely to depend on the agent you talk to - I doubt anyone in this forum will be able to confirm that you will be on the earlier flight.

Good luck! (I think you are going to need it with this one).