Rules Question: How would these 2 scenarios work out?

Say [[Koma, Cosmos Serpent]] is sacrificing a creature to tap down one of my creatures. If I cast [[Deadly Rollick]] to kill it, would it still tap my creature? Also, say the stack is full of effects and triggers from a permanant, can I interupt and kill the creature to stop the triggers, or do they still resove? Also when does damage happen on the stack?? Does it wait until everything resolves? I'm new to the game, thanks for any help.