Jessica Chastain has a topless scene with Tom Hardy in “Lawless,” but the Juilliard grad says school helped her overcome shyness. “You’d get up in front of everyone and have to sing ‘Happy Birthday’ [very slowly] . . . and look everyone in the face — and I’d be beet red. You make a fool of yourself over and over. Now I’m like, ‘Well, this is not gonna be as humiliating as Drama Room 304 at Lincoln Center.’ ” At Tuesday’s premiere, Harvey Weinstein praised the actors’ performances and declared, “The Oscar race starts tonight.”