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.
Lady Macbeth of the Mtsensk District (opera) Lady Macbeth of the Mtsensk District (Russian: "Леди Макбет Мценского уезда" , or "Ledi Makbet Mtsenskogo uyezda") is an opera in four acts and nine scenes by Dmitri Shostakovich, his Opus 29. The libretto, jointly written by Alexander Preys and the composer, is based on the novel of the same name by Nikolai Leskov. (The opera is incorrectly named "Lady Macbeth of Mtsensk" on several commercial CD and DVD recordings.)