Batman is of course one of the main characters. He is the central figure around which the story revolves. Bane is another major character. He is the one who causes Batman's downfall in a physical sense. Robin also plays an important role. He has to deal with the situation after Batman is incapacitated.
That's a tough one! But many fans consider Batman from 'The Dark Knight Returns' to be one of the best. He's shown as a grizzled, experienced, and determined hero.
The identity of the new Batman in the comics changes over time. It might be a previously established character taking on the mantle or a completely new creation. You'd need to check the current storylines to find out exactly.
Currently, Batman in the comics is still Bruce Wayne. However, there have been alternate timelines and universes where other characters have taken on the Batman mantle for brief periods or in specific storylines.
In most comic storylines, Batman hasn't been killed. But there might be alternate universes or special story arcs where such a thing could happen, though it's not a common occurrence.