I'll be flying on CX107 on 30th May.
From now till the impending changeover from 3 class (sold as 2) A34C to A34D, the First Class section of those flights are 'blocked' by Quality Control. These seats cannot be pre-reserved by anyone, and are released by QC to top tier members of the Marco Polo Club 3 days prior to the departure. Or if you have an asia miles account, you may check-in on line during those 3 days prior to departure and it 'may' open up to you.
Having an AA F award will not make any difference until you're at the airport. If CX allows you through check-in from wherever you are, then maybe that will work. Otherwise you might just have to request a change of seating at HKG only.