the first place you should go is our Wiki. Top thread and it's sticky. You can find every aircraft type and what CX calls it there, ie 77H, 77G, 33K, etc.

Then, after doing that you should just search flight schedules.

If still not sure you can check the seatmap of your flight and align it with the official CX seatmaps you can find in google.

CX flies many regional routes regularly with long-haul aircraft. Their LH fleet is significantly larger than their SH fleet. However, the schedules change over time, and there are also equipment swaps even when the schedule is fixed. But it's very, very common for LH planes to fly regional routes and for them to be fixed in the schedule well in advance. Just fyi CX is okay swapping them out if something happens so I wouldn't put too much emotional equity into it, as folks are routinely coming here disappointed that such and such plane got swapped out.

Fyi, every flight to/from Hong Kong is international. the term you can search for here is "long-haul", abbreviated to "LH". that acronym is, unfortunately, unsearchable.