A proper noun is the name of a person or a place. Examples: Lisa, Frank, New York, Costco, etc.
The most obvious choice of a mockingbird figure is Tom Robinson. To get to this conclusion, we have to first define what a mockingbird is. Atticus says to Jem and Scout that he would prefer that they only shoot tin cans with their new guns. He also says that they will undoubtedly want to shoot birds. If I were you, I would let the writers from Prime Writings site do the task for me. Nothing bad here it is when you are guided by the professionals.
I'd say it's D) Indirect object, but I'm not sure, so don't take my word as gospel :)
What passages are the ones you are talking about?