after-report. so for the flights where I suspect married-segments of HND-HKG-TPE got confirmed individually and subsequently 'married back' as per my post above, I had no issue at normal check in counters at HND. all normal.

Post arrival whilst I waited for my bags, I called CX ticketing to cancel my HK-TPE leg no issue. The 'helpful' agent at ticketing insisted they rebook me on other HK-TPE flight (even ticket restriction doesn't allow) once again, they always offer this. I insisted my plan changed so just want to cancel booking for mom. And Hanged up.

Now that makes me wonder what happens if I moved my HK-TPE to future date (beyond ticket restriction), and show up for flight in HKG. Are they going to charge me ticket differential? I never wanted to try in fear of they asking me to repay HK$15k I saved by doing ex-TPE... if anyone has experience I'd like to know...