Which opera has more acts, Der Rosenkavalier or Manon? 
Der Rosenkavalier: Der Rosenkavalier (The Knight of the Rose or The Rose-Bearer), Op. 59, is a comic opera in three acts by Richard Strauss to an original German libretto by Hugo von Hofmannsthal. Manon: Manon (] ) is an "opéra comique" in five acts by Jules Massenet to a French libretto by Henri Meilhac and Philippe Gille, based on the 1731 novel "L’histoire du chevalier des Grieux et de Manon Lescaut" by the Abbé Prévost.
Manon