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Pretty much what CanucksHKG said,
1. if you are continuing on the same flight to JFK then you will need to disembark the aircraft and wait for about 50min in a designated waiting area for the aircraft to be ready for flight to JFK. so you won't be able to use any of the lounges. The only lounge in JFK T7 is the BA Galleries. It's not bad, but not great either.
2. Yes, you will be able to use any of the OW lounges in HKG, although The Wing F is generally recommended