A Life for the Tsar is a  Russian libretto with four acts, Tosca an Italian libretto has how many acts?
A Life for the Tsar A Life for the Tsar (Russian: Жизнь за царя , "Zhizn' za tsarya"), as it is known in English, although in Soviet times its name was "Ivan Susanin" (Russian: Иван Сусанин ) is a "patriotic-heroic tragic opera" in four acts with an epilogue by Mikhail Glinka. The original Russian libretto, based on historical events, was written by Nestor Kukolnik, Egor Fyodorovich (von) Rozen, Vladimir Sollogub and Vasily Zhukovsky. It premiered on 27 November 1836 OS (9 December NS) at the Bolshoi Kamenny Theatre in St. Petersburg. The historical basis of the plot involves Ivan Susanin, a patriotic hero of the early 17th century who gave his life in the expulsion of the invading Polish army for the newly elected Tsar Mikhail, the first of the Romanov dynasty, elected in 1613.
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).