Short answers, pulled from the story.
Stalinist architecture began in February 1931 when major Soviet architects received invitations to bid for the Palace of Soviets design. The style transitioned from free-wheeling experimentation to rigid state control within two years by September 1933.
The Seven Sisters are eight identified construction sites for Moscow skyscrapers that Stalin issued an idea to build in 1946. By September 1947, eight sites were identified but the eighth site in Zaryadye was eventually cancelled while the others stood on concrete slab foundations with overengineered steel frames.
Leonid Polyakov designed Oktyabrskaya station like a Classicist temple while Kievskaya station became the first to employ mosaic stone floors in 1938. Mayakovskaya station opened in 1938 with elaborate decorations and Arbatskaya station became the longest in the system at 250 meters instead of the standard 160.
Poland features the Palace of Culture and Science designed by Lev Rudnev while East Germany saw grandiose war memorials built in Berlin including one in Tiergarten and another larger one in Treptow. Romania produced the Palace of the Parliament under Ceaușescu starting in 1984 and completed in 1997.
Stalinist architecture coexisted with luxury empire until November 1954 when critics openly criticized excesses. The last Stalinist building, Hotel Ukrayina in Kiev, finished in 1961 which marked the end of all late Stalinist construction.