Composed for Carnival in 1709, Handel’s path-breaking opera Agrippina marked the 24-year-old composer’s first operatic masterpiece, establishing his international reputation and setting the course for future triumphs. Juilliard Opera offers one concert performance at Alice Tully Hall on February 11 and three staged performances in the black-box setting of the Willson Theater on February 18, 20, and 22.