Elementalist Adept

Prowess is a triggered ability. “Prowess” means “Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.”

If a creature has multiple instances of prowess, each triggers separately.

Flash is a static ability that functions in any zone from which you could play the card it’s on. “Flash” means “You may play this card any time you could cast an instant.”

Multiple instances of flash on the same object are redundant.