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.
Aida Aida (] ) is an opera in four acts by Giuseppe Verdi to an Italian libretto by Antonio Ghislanzoni. Set in Egypt, it was commissioned by and first performed at Cairo's Khedivial Opera House on 24 December 1871; Giovanni Bottesini conducted after Verdi himself withdrew. Today the work holds a central place in the operatic canon, receiving performances every year around the world; at New York's Metropolitan Opera alone, "Aida" has been sung more than 1,100 times since 1886. Ghislanzoni's scheme follows a scenario often attributed to the French Egyptologist Auguste Mariette, but Verdi biographer Mary Jane Phillips-Matz argues that the source is actually Temistocle Solera.