CX and North American segments
 

CX flies HKG-JKF and HKG-YYR, and the first one stops over in ANC and the latter in YVR. Are the North American legs bookable, so that I can use CX on ANC-YYZ or YVR-JFK segments in NA?

Yes to the YVR-JFK segment. I'm not sure about the ANC-YYZ segment but I recall something about this not being possible. Hopefully, others will have more specific information.

No. It's a technical stop to change crews and refuel if they need to. Not all flights actually even stop there, iirc.

yes to YVR-JFK
no to ANC-YYZ

the difference is that YVR-JFK is fifth freedom, and the canadian govt ok'ed it.

while anc-yyz is only a re-fueling stop, and the american didnt allow it.
(note for KE/OZ/CI, they can drop off * pick up pax in ANC on route to JFK. i think it is a result fo negotiation)