Short answers, pulled from the story.
Russian citizen Igor Girkin led a heavily armed unit of fifty volunteers from the Russian Armed Forces to seize Sloviansk. This commando group arrived from occupied Crimea without insignia and attacked local administration buildings within hours.
Pro-Russian militants captured Sloviansk on the 12th of April 2014 using a unit led by Igor Girkin. The group set up roadblocks and seized weapons from local arsenals immediately after taking control of the town.
Malaysia Airlines Flight 17 was shot down by a Buk surface-to-air missile originating from Russia's 53rd Anti-Aircraft Missile Brigade. Investigations confirmed the launcher was transported from Russia on the day of the crash and returned afterward, leading the Netherlands and Australia to hold Russia responsible for all 298 deaths.
About fourteen thousand people died during the war in Donbas between 2014 and 2022 including six thousand five hundred Russian or proxy forces and four thousand four hundred Ukrainian soldiers. Three thousand four hundred civilians also perished with most casualties occurring within the first year of fighting.
Russia recognized both the Donetsk People's Republic and Luhansk People's Republic as independent states on the 21st of February 2022. The following day Russia initiated a full-scale invasion of Ukraine subsuming the regional conflict into broader hostilities.