1. I think Neil still would've committed suicide even if Mr. Keating hadn't came into his life, because he couldn't stand up to his dad. He also would've choose acting and wouldn't have told his dad and it all would've ended the same way.
2. Bravest would have to be Knox or Todd, Knox is brave the whole movie and he does whatever he wants and says what he feels, Todd is very brave at the end, no one would've done what he did and I think that makes him very brave.
3. I think Mr. Keating put it in the room so that someone would see it and take it into consideration and live by that book and to teach them to do what they say and to seize the day.