Which opera, if any,  Venus and Adonis or Bluebeard's Castle has more acts ?
Bluebeard's Castle Bluebeard's Castle (Hungarian: A kékszakállú herceg vára ; literally: "The Blue-Bearded Duke's Castle") is a one-act opera by Hungarian composer Béla Bartók. The libretto was written by Béla Balázs, a poet and friend of the composer, and is written in Hungarian, based on the French literary tale "La Barbe bleue" by Charles Perrault. The opera lasts only a little over an hour and there are only two singing characters onstage: Bluebeard ("Kékszakállú "), and his new wife Judith ("Judit " ); the two have just eloped and Judith is coming home to Bluebeard's castle for the first time.
La caverne (Méhul) La caverne ("The Cavern") is an opera by the French composer Étienne Méhul. It takes the form of a "comédie en prose" in three acts. It premiered at the Opéra-Comique, Paris on 5 December 1795. The libretto, by Nicolas-Julien Forgeot, is based on incidents from the novel "Gil Blas" by Alain-René Lesage.