Which opera, if any,  Venus and Adonis or Bluebeard's Castle has more acts ?
Venus and Adonis (opera) Venus and Adonis is an opera in three acts and a prologue by the English Baroque composer John Blow, composed in about 1683. It was written for the court of King Charles II at either London or Windsor. It is considered by some to be either a semi-opera or a masque, but "The New Grove" names it as the earliest known English opera.
Sir John in Love Sir John in Love is an opera in four acts by the English composer Ralph Vaughan Williams. The libretto, by the composer himself, is based on Shakespeare's "The Merry Wives of Windsor" and supplemented with texts by Philip Sidney, Thomas Middleton, Ben Jonson, and Beaumont and Fletcher. The music deploys English folk tunes, including "Greensleeves". Originally titled "The Fat Knight", the opera premiered at the Parry Opera Theatre, Royal College of Music, London on 21 March 1929. Its first professional performance was on 9 April 1946 at Sadler's Wells Theatre.