Upper Hand

Only deals damage and causes the target to flinch if the target has selected a Physical or Special category move with an increased priority

Upper Hand only deals damage and causes the target to flinch if the target has selected a Physical or Special category move with an increased priority from +1 to +3.
Otherwise, it fails.
Pokémon with the ability Inner Focus or those behind a Substitute cannot be made to flinch.
Upper Hand has an increased priority of +3 meaning that it will be used before most other moves.
If another Pokémon uses a move of the same priority, the Pokémon with the higher Speed will go first as usual.
This effect also considers abilities that change the priority of moves such as Gale Wings.