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.
Le faucon (opera) Le faucon (English: The Falcon , Russian: Сокол ) is an "opéra comique" in three acts by the Ukrainian composer Dmitry Bortniansky with a French language libretto by Franz-Hermann Lafermière. It was first performed on 11 October 1786 at the Gatchina Palace in Russia by aristocratic amateur singers. The plot is borrowed from Boccaccio's "The Decameron" (Fifth Day, 9th tale) which also served as the basis for Pierre-Alexandre Monsigny's 1771 comic opera "Le faucon" (libretto by Michel-Jean Sedaine) (and later for Gounod's "La colombe").