Hi fellow flyers, I need your wisdom.

Situation:
I currently hold return portion of open B-Class ticket, YVR to HKG. I also have reservation for M-class ticket, starting with HKG-YVR with ongoing 3 segments to Australia.

I can make a booking for B-class on the day I want to leave (21st, Dec) for HKG. However, for M-class ticket, I only have bookings for the day prior to my intended travel date (19th).

I would like to use the B-Class ticket to travel to HKG from YVR so that I can travel on the day I want. Consequently, I will also forfeit the first segment of my M-class ticket (19th, YVR-HKG).

Question:

1) Do airline ticketing rule allow me to do this?
2) Even if the rule allows, will my reservation for the ongoing 3 segments be cancelled automatically if I do not show up for the first segment? I will ask CX to make a notice on my file, but I fear that Checkin agents will do not bother read through my file remarks, and simply cancel all of my bookings.

Your advise is appreciated! Thanks

Ted