I'm looking at creating a Qinggong monk NPC and was wondering I swap out Slow Fall for the Barkskin Ki Power at level 4 does it meet Arcane Strike's prerequisite of 'Ability to cast arcane spells'?
Just as the rogue cannot use Minor Magic to qualify for Arcane Strike, the monk cannot. Arcane Strike requires arcane spells, not spell-like abilities or supernatural abilities.
Spell like abilities are not the same thing as a caster level. They don't cast spells, they use spell like abilities that resemble spells. Hence they don't get a caster level.