I am an attorney, and the answers are "no" and "no". The jury decides facts, not law, and it is the judge's job to instruct the jury as to what facts constitute a crime. Bad instructions often result in bad verdicts.
A prosecutor's job is to promote justice, which many, many times involves deciding not to indict someone despite them being "accused" of a crime. They simply decide on their own they don't think the conduct is illegal, or that it isn't worth prosecuting, or that the facts don't support it.
Sort of like Bragg did before he didn't.
Sometimes the head of the FBI pretends he is the AG and tells us why an individual was not indicted.