Why Is Corrado Soprano Called Junior?

According to series creator David Chase the name Junior was taken from one of his own older cousins. Chianese had landed the role of Junior over Tony Sirico who plays Paulie Gualtieri, and Frank Vincent who plays Phil Leotardo.

Who JR underboss?

Aside from underboss Joseph Sasso, and captain Lorenzo Barese's arrest, 13 others were indicted. It can be assumed that many of the arrested were part of or associated with Junior's Crew.

Who did JR think Tony when he shot him?

Junior descends the stairs and, believing his nephew to be Malanga, shoots Tony in the abdomen. Panicking, Junior runs upstairs, hiding away in his bedroom closet while Tony struggles to dial 911 before losing consciousness.