Short answers, pulled from the story.
The Bolsheviks convened a separate congress and declared the first Soviet Republic of Ukraine on the 24th of December 1917. Warfare ensued against the Ukrainian People's Republic for the installation of the Soviet regime in the country with direct support from Soviet Russia.
A combination of factors including Soviet policies of compulsory grain requisitions, forced collectivization, dekulakization, and Russification caused the Holodomor famine. The policy resulted in an estimated loss of human life between 2.6 million to 10 million people due to starvation and exported grain to the West.
During World War II the Soviet Union lost about 8.6 million combatants and around 18 million civilians, of these 6.8 million were Ukrainian civilians and military personnel. An additional 2.2 million Ukrainians were sent to forced labour camps by the Germans while 3.9 million were evacuated to the Russian Soviet Federative Socialist Republic.
The Supreme Soviet of Ukraine declared independence on the 24th of August 1991 following the failed August Coup in Moscow. A referendum on independence was held on the 1st of December 1991 where 92.3% of voters voted for independence nationwide.
Aleksey Kirichenko succeeded Leonid Melnikov as First Secretary of the CPU on the 4th of June 1953. This appointment marked a significant change since Kyrychenko was the first ethnic Ukrainian to lead the party since the 1920s.