A Life for the Tsar is a  Russian libretto with four acts, Tosca an Italian libretto has how many acts?
Tosca Tosca (] ) is an opera in three acts by Giacomo Puccini to an Italian libretto by Luigi Illica and Giuseppe Giacosa. It premiered at the Teatro Costanzi in Rome on 14 January 1900. The work, based on Victorien Sardou's 1887 French-language dramatic play, "La Tosca", is a melodramatic piece set in Rome in June 1800, with the Kingdom of Naples's control of Rome threatened by Napoleon's invasion of Italy. It contains depictions of torture, murder and suicide, as well as some of Puccini's best-known lyrical arias.
Leben des Orest Leben des Orest ("The Life of Orestes") is a grand opera in five acts (eight scenes) with words and music both by Ernst Krenek. It is his Op. 60 and the first of his own libretti with an antique setting. The score is inscribed with the dates of composition: 8 August 1928 – 13 May 1929, and includes indications of recommended cuts made for the first production. It premiered at the Neues Theater in Leipzig on 19 January 1930, and opened at the Kroll Opera House in Berlin in early March of the same year (Leichtentritt 1930, 366).