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.
Motezuma Motezuma is an opera in three acts by Antonio Vivaldi with an Italian libretto by Alvise Giusti. The libretto is very loosely based on the life of the Aztec ruler Montezuma who died in 1520. The first performance was given in the Teatro Sant'Angelo in Venice on 14 November 1733. (In earlier reference books the opera is referred to as "Montezuma", but since the reappearance of the original manuscript this has been corrected to "Motezuma".) The music was thought to have been lost, but was discovered in 2002 in the archive of the music library of the Sing-Akademie zu Berlin. Its first fully staged performance in modern times took place in Düsseldorf, Germany, on 21 September 2005.