Liberty has $69 group lessons (min 4 need to sign up), $345 for a one hour rental of the wave or the Ultimate experience for $552 (one hour rental + instructors).
Depends on if it's the embarkation port or just a visiting port. For a regular port stops that's fine, for an embarkation port you want to be there a bit earlier.
Yes, but you have to wait to do that on board - I don't see it available in the app and don't recall ever being listed in the planner but it is listed at the venue.