@Cypher27
Since the Purson clan assisted in creating the attention-diverting glasses that Crocell wears, I'd say it seems likely that at least some analogous magic can be used, even if it's not the real thing. Though I'm not sure if it's actually learning their skill, or if it's just learning something to replicate it.
As far as the archery goes, my interpretation was always that we have:
Mini Sensei: Fully inherited main branch ability who can fire 1000 arrows and hit every time.
Robin Sensei: Partially inherited side branch ability, can only fire 3 arrows that are guaranteed hits, but maybe he has longer range or something?
Iruma: Taught how to form a bow with magic, but his archery ability is completely dependent on his own skill.