Platform Side Scroller enemy AI

I was wanting to make detailed platform side scroller and have figured out health and attacks, i just do know know how to make my enemy have AI where he chases the player when the player is on his platform and attack when he is near, patrolling is optional, so is having him chase the player only when the player is on his platform, but it is preferred

This makes enemy follow player anywhere (enemy has to be a platformer too).

is there anyway to make it so that when the enemy dies, he will become neutral and fall down and be able to add multiple individual enemies without making tons of enemies?