I can’t decide what risk to rather take?

1) book CX F JFK-HKG close in (if 2F are available) than cancel and rebook for next year for required dates (when they open up).

2) book for next year's desired dates one F & one J & hope another F opens up for the desired date.

3) or maybe book one for the desired date & one for another date & cancel.

What do you think?

If you are booking close in, then you will need to change dates real soon anyway, so how will that help you get your desired dates?

It really depends on how far out your desired dates are and if J is available. If one F and one J is available, I'd book one of each on the desired flight and hope another F opens up close in. Worst case you still have J.