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.
Loreley (opera) Loreley is an opera ("azione romantica") in three acts composed by Alfredo Catalani to a libretto by Angelo Zanardini, Carlo D'Ormeville and others. It premiered on 16 February 1890 at the Teatro Regio in Turin. Based on the German legend of the Lorelei, the opera is an extensive reworking of Catalani's four-act opera "Elda" which had premiered in Turin ten years earlier.