Short answers, pulled from the story.
Ascanio in Alba, K. 111, is a pastoral opera in two parts (Festa teatrale in due parti) composed by Wolfgang Amadeus Mozart to a libretto by Giuseppe Parini. It was written in 1771, when Mozart was fifteen years old.
Empress Maria Theresa commissioned Ascanio in Alba to celebrate the wedding of her son, Archduke Ferdinand Karl, to Maria Beatrice d'Este on the 15th of October 1771. The opera was designed as a ceremonial court entertainment tied to the Habsburg dynastic occasion.
Ascanio in Alba premiered at the Teatro Regio Ducale in Milan on the 17th of October 1771, two days after the wedding it celebrated.
Giovanni Manzuoli, a mezzo-soprano castrato, sang the role of Ascanio at the premiere on the 17th of October 1771. Geltrude Falcini sang Venus and Antonia Maria Girelli Aguilar sang Silvia.
The opera is set at the mythical site of Alba Longa near Rome. Venus sends her son Ascanio to rule there but instructs him to approach his betrothed, the nymph Silvia, in disguise to test her virtue. Silvia remains faithful even in grief, believing the disguised stranger is not Ascanio. Venus descends at the end to unite the couple and reveal that the test was meant to prove Silvia's constancy.
Four recordings document the opera: a 1959 recording with the Angelicum di Milano under Carlo Felice Cillario; a 1976 Salzburg recording with Agnes Baltsa and Edith Mathis under Leopold Hager (released on CD in 1991); a 1990 Naxos recording with Michael Chance and Jill Feldman under Jacques Grimbert; and a 2002 Brilliant Classics recording featuring Maaike Beekman and Claron McFadden.