It could be a 4 class 777 with 3 class service. Whether F cabin gets used depends on load and crew numbers. As this isn't a route that normally has an F cabin, if the F seats are used it would be with J service.

If this is the case, seat selection into F cabin may not be possible at all or until T-24 or even at airport.

Anyway, I'm sure someone will be along in a minute who can check what plane is going to be used.