Originally Posted by LchChester

Those are airport codes.

My point is even there are availability for both Manila to Hong Kong and Hong Kong to Vancouver, it doesn't necessarily follow that flight is available from Manila to Vancouver via Hong Kong due to something called married segment.

I would say the chance for redeeming economy class on the flights back to Vancouver are not high. Btw, you may considering ask the agent about the premium economy cabin because it does not show up on their page even there is availability, and the mileage difference between economy and premium economy is small.