Which rudder input is correct?

The recovery: PARE

The Airplane Flying Handbook says to always follow the manufacturer's recommended spin recovery procedure. When one isn't available, the handbook gives a general procedure. The memory aid PARE covers it: Power idle, Ailerons neutral, Rudder opposite the direction of rotation, Elevator briskly forward. PARE works for almost all airplanes, but it's worth checking against the POH before flight.

The rudder is the key control input to arrest the rotation. It's full rudder, opposite the direction of rotation, held until the rotation stops.

Which way is it spinning?

The turn coordinator is the most reliable instrument for determining the direction of rotation. In this reel it shows a turn to the left, so the correct input is full right rudder.

Why not the ball?

The ball isn't reliable in a spin. It measures lateral acceleration, and which way it moves depends on where the instrument is mounted. The Airplane Flying Handbook puts it this way: "The location of the instrument in the airplane determines how the ball will move rather than the direction of the spin." The handbook also says the pilot should not use the ball to determine spin direction.

When does the rudder go neutral?

Only after the rotation stops. Neutralizing the rudder is a later step in the recovery. Until the rotation stops, it's full opposite rudder.