You can do whatever you want; upon settling in, the purser will come and take your order - you can make requests now if you want to ensure what you want later will still be available

Generally, I will substitute breakfast for dinner on flights where CX treats the meal times as if it were still HK time; for example, the CX888 to YVR serves breakfast for the second meal before landing where it's 8pm in YVR - this doesn't make any sense to me as I generally get off this segment but it is breakfast time in HK

Other times, there are instances were I would break the meal up into two; YVR to JFK and vice versa, I would ask to have the apps, main and dessert as the main course and then soup and cheese 60 min before landing. The FAs will come by as requested and see if you still want the second meal. Personally, I split the meals as I generally eat before going to the airport for those two flights and will be starving by the end of the flight - otherwise, I still have an abbreviated meal on board and tell the FA that I'd like to skip the soup and cheese when they come by again.