As I recall
16: new model
17: almost the same
new muffler shield and revised air intake, both available from Honda as upgrades to 2016
Added seat belt speed limiter
18: added the Le model and i4wd
Added the radiator air deflector, can be added to earlier models
Added more underseat heat shielding, was a product improvement for earlier models
Changed the trailer hitch pin and added the upper gusset, can not be added to earlier machines
19:. Nothing
20:. Nothing
21:. New phantom camo.
22: maybe lots of things but no production dates