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.
Senza sangue Senza sangue (Without blood) an opera in one act by Péter Eötvös with a libretto by Mari Mezei. It is based on the second part of the novel of the same name by Alessandro Baricco and is intended to be performed jointly with Béla Bartók's one-act "Bluebeard's Castle". The concert première was given by the Cologne Philharmonic Orchestra on 1 May 2015. It was premièred in full on 15 May 2016 at the Festival d'Avignon. It is his tenth opera. Anne Sofie von Otter, who gave the New York première with the New York Philharmonic, said: "“The piece is not at all easy for the two singers... [It’s] hard to find the pitch; you have to work it into the voice, unless of course you happen to have perfect pitch, which I don’t."