These questions ask for your opinion. The only one that is not an opinion question is the first one. Do you have a class reading that you are supposed to read in order to answer this?
I think you should look at an article by Steiker called "No, capital punishment is not morally required.
Also, google this: Sunstein and Vermeule.
Also, Google this: What did Kant say about the death penalty?
I don't want to give my opinion, because you have to form your own. Go read about it, and if an article has some sections you don't understand, ask us about them.