If Lycanroc's third form does exist, It might be the ace.
Jangmo-o can't learn Sky Uppercut, but it can learn Sky Uppercut when it evolves into Hakamo-o.
I don't think writers are giving any Ash's Pokemon four powerful moves. Incineroar can have least two powerful moves (Darkest Lariat and Fire Blast/Cross Chop).
I hope it will learn Flame Charge instead of Flare Blitz. Why? Using Flame Charge can increase Incineroar's speed and Ash is not good with slow + defenseless Pokemon. (Torracat is so fast, but Incineroar is very slow)
I doubt Fire Fang will be replaced, this move is last move Stoutland taught Litten how to use..
Cross' Incineroar used Fire Fang in M20, so it doesn't need to use its mouth/fang to use it.
Why didn't you give Alolan Sandslash Rapid Spin/Gyro Ball? It is so fast with spinning. And it can't learn Ice Beam.
Yeah, we can't predict the third form's moveset without knowing its moves pool.