Which opera has more parts including acts and tableaux, Le roi d'Ys or Stiffelio?
Stiffelio Stiffelio is an opera in three acts by Giuseppe Verdi, from an Italian libretto by Francesco Maria Piave. The origin of this was the novel “Le pasteur d’hommes”, by Émile Souvestre, which was published in 1838. This was adapted into the French play "Le pasteur, ou L'évangile et le foyer" by Émile Souvestre and Eugène Bourgeois. That was in turn translated into Italian by Gaetano Vestri as "Stifellius"; this formed the basis of Piave's libretto.
Polyxène et Pirrhus Polyxène et Pirrhus ("Polyxena and Pyrrhus") is an opera by the French composer Pascal Collasse, first performed at the Académie Royale de Musique (the Paris Opéra) on 21 October 1706. It takes the form of a "tragédie lyrique" in a prologue and five acts. The libretto is by Jean-Louis-Ignace de La Serre.