Short answers, pulled from the story.
At least 6 million people were affected by internal forced migrations in the Soviet Union between 1930 and 1952. Of this total, 1.8 million kulaks were deported in 1930-31, 1.0 million peasants and ethnic minorities in 1932-1939, and about 3.5 million ethnic minorities were further resettled during 1940-52.
Soviet Koreans were the first entire nationality to be mass-transferred in the Soviet Union. In October 1937, nearly the entire Soviet ethnic Korean population of 171,781 people was forcibly moved from the Russian Far East to the Kazakh SSR and Uzbek SSR.
Estimated deaths from Soviet deportations range from 800,000 to 1,500,000 people. Soviet archives documented 390,000 deaths during kulak forced resettlement and up to 400,000 deaths of people deported during the 1940s, but historian Nicolas Werth places overall deaths closer to 1 to 1.5 million.
Yes, by multiple governing bodies. The deportation of Crimean Tatars is recognized as genocide by Ukraine, Latvia, Lithuania, and Canada. The European Parliament recognized the deportation of Chechens and Ingush as genocide in February 2004.
Formal rehabilitation began in 1956 following Khrushchev's condemnation of the deportations. Decrees lifting restrictions on specific groups were issued between January and July 1956, though all initially denied the right of return. National autonomies for Kalmyks, Chechens, Ingush, Karachais, and Balkars were restored in 1957 and 1958.
More than 200,000 people were deported from Latvia, Lithuania, and Estonia between 1940 and 1953, and at least 75,000 more were sent to the Gulag. Ten percent of the entire adult Baltic population was deported or sent to labor camps. By 1989, native Latvians made up only 52% of Latvia's population and native Estonians made up 62% of Estonia's.