Maybe not directly relevant to MPC, but I am really curious about HK Immigration Policy. I have Taiwan and US dual (two different first names), and most of my FFPs (including TK and AA) on Taiwanese name. If I book a ticket to HK using my Taiwan name, would I go into trouble if I use US passport to clear Hong Kong border? What about on the way out? Can I just show them both and explain why I have Taiwanese name on boarding pass but using American passport with a different name?
HK immigration doesn't care about your boarding pass or ticket. You can enter and exit using your US passport with no problem in that respect.
The problem is that you need to show the airline that you have the right documents to enter your destination country.
Since your tickets are in your Taiwan name, you always need to show the airline your Taiwan passport.
But you can't enter HK on your Taiwan passport unless you apply for an online approval and print it out, whereas you don't need any prior approval to enter with your US passport.
So if you are flying to HK, then you either need to register with your Taiwan passport (in which case you might as well just use it to enter HK), or you have to show the airline both passports and tell them you will use the US passport to enter.
If you are flying from HK to the US, then you won't have a US visa in your Taiwan passport, so you would have to show the airline both passports too. This also applies for anywhere which allows US citizens visa-free entry, but not Taiwan/ROC citizens.
Whether airlines will accept two passports with different names, I can't say.
When departing HK, there is a passport and boarding pass check run by the airport. This is not immigration. It is before you pass through security into the secure area. Exit immigration is after security.
At this boarding pass check, you need to show a passport which matches the name on the boarding pass, which is all they care about. So you would always show your Taiwan passport here and never your US passport. After security, the passport you use at the actual exit immigration is the same one you used to enter HK.
If you are going between HK and Taiwan, then you can still use the US passport to enter and exit, but you won't need to show it to anyone except HK immigration.