Short answers, pulled from the story.
Stalinist architecture, also called socialist classicism, is a movement in architecture, monumental art, and decorative art that dominated the USSR and the wider socialist bloc from the mid-1930s to the mid-1950s. It combined elements of classicism, baroque, the Napoleonic Empire style, and Art Deco, characterized by strict symmetry, emphasized monumentality, and abundant Soviet ornamentation.
The Seven Sisters are a set of high-rise buildings constructed in Moscow between 1947 and 1957, including the Main Building of Moscow State University, residential towers on Kotelnicheskaya Embankment and Kudrinskaya Square, the Ministry of Foreign Affairs, the Ministry of Transport Construction, and the Ukraina and Leningradskaya hotels. Designed at Stalin's initiative to mark Moscow's 800th anniversary, they are defined by stepped silhouettes crowned with tall spires bearing Soviet symbols.
Stalinist architecture was officially ended by the decree On liquidation of excesses, issued on the 4th of November 1955. The decree estimated that stylistic excesses had added 30-33% to total construction costs, and it ordered a shift to standardized designs and prefabricated construction. The last Stalinist building, the Hotel Ukrayina in Kiev, was completed in 1961.
The Palace of Soviets competition, held between 1931 and 1933, was the crucible in which Stalinist style took form. All modernist entries were rejected by February 1932, and Boris Iofan's neoclassical draft received public approval in May 1933. A 1932 memorandum Stalin wrote from Sochi, selecting Iofan's design and proposing specific changes, was not published until 2001 and remains the key document for understanding Stalin's personal influence on architectural policy.
Forced labor was central to several major Stalinist infrastructure projects. The Moscow Canal, built between 1932 and 1937, was constructed by gulag prisoners. The Volga-Don Canal, completed in 1952, was built predominantly by prisoners held in specially organized corrective labor camps; during 1952 the number of convicts employed exceeded 100,000.
From about 1948 to 1956, Stalinist architecture was adopted across the Eastern Bloc, usually after internal modernist opposition was defeated. Notable examples include Lev Rudnev's Palace of Culture and Science in Warsaw, the Stalinallee in East Berlin, the Latvian Academy of Sciences in Riga, and the Spark Building in Bucharest. Similar towers and embassy buildings appeared as far as North Korea, China, and Helsinki, Finland.