I am back and let me share with you my experience on this VN/CX code share drama

Outbound online check-in:
CX freaked me out on this as they didn't allow me to check in, so I gave them a call. The result was a complete freak out as the agent said my booking had issue and I might not even board the plane. Ran to VN office the next day and they said no issue at all. I even put them on conference call and the CX agent kept blaming VN for their wrong doing. It was a complete disaster. Magically within the 24 hours prior departure, I could check in at CX website, so not sure if this check-in time frame aligning to VN's 24 hours online check in practice.

Outbound seat selection:
As I had no way to input my MPC number, so I couldn't select any seats, but the system already allocated a pair of seat for me and my child.

Airport check-in:
As I was told my booking having certain issues, I arrived at the airport 3 hours ahead. No issue at all. I could check in at the F desk

Wing F lounge access:
Despite my flight was marketed by VN, I was able to enjoy full F benefit