Yes. Hydrochloric acid and muriatic acid are the same thing. Muriatic acid is just the old name for it and isn't used much anymore.
Yes.
Hydrochloric acid is made of hydrogen and chlorine. Nitric acid has nitrogen in it. As hydrochloric acid has no nitrogen in it, you cannot make nitric acid from hydrochloric acid. (As far as I know)
No, they are different compounds, but are in the same group(i.e. acids)
Yes: 3 parts hydrochloric acid (HCl) and 1 part nitric acid (HNO3)