Short answers, pulled from the story.
Lucio Silla premiered on the 26th of December 1772 at the Teatro Regio Ducale in Milan. Mozart was sixteen years old and conducted the premiere himself. The production was described at the time as "a moderate success."
The libretto was written by Giovanni de Gamerra and revised by Pietro Metastasio. Metastasio was one of the most influential opera librettists of the eighteenth century.
Lucio Silla is an opera seria in three acts based on the Roman dictator Lucius Cornelius Sulla. The plot follows Sulla's pursuit of Giunia, the daughter of his murdered enemy Gaius Marius, while her true love, the exiled senator Cecilio, attempts to return to Rome. The opera ends with Sulla pardoning his enemies, freeing Cecilio, and abdicating as dictator.
Lucio Silla was Mozart's last opera written in Italy and the first of his stage works to make full use of recitativo accompagnato, a key feature of opera seria. Scholars including Téodor de Wyzewa and Georges de Saint-Foix described it as a "grande crise romantique," marking a new emotional depth in the composer's output.
The 1980 recording conducted by Leopold Hager with the Mozarteum Orchestra Salzburg, featuring Júlia Várady as Cecilio and Arleen Augér as Giunia, is regarded as the most complete recording and the reference version of the opera. It was released on Deutsche Grammophon and reissued in 1991 as part of the Complete Mozart Edition on Philips.
The ballet Le gelosie del Serraglio, K. 135a, was choreographed by the French dancer Jean-Georges Noverre. The completed score of the ballet is lost, though a few sketches survive. Mozart worked with Noverre again in Paris in 1778.