Short answers, pulled from the story.
The Christianization of Kievan Rus' began in 988 when Grand Prince Vladimir the Great was baptized by clergy from Constantinople. This event marked the start of Orthodox Christianity as the state religion for the region.
A council of Russian bishops elected Jonah as metropolitan on the 15th of December 1448, which marked the beginning of autocephaly for the Russian Church. The move was later justified by interpreting the fall of Constantinople in 1453 as divine punishment.
Between 1917 and 1935, 130,000 Eastern Orthodox priests were arrested with 95,000 executed. Many victims became recognized saints known as new martyrs and confessors of Russia.
Metropolitan Kirill of Smolensk was elected Patriarch of Moscow and All Rus' on the 27th of January 2009 receiving five hundred eight votes out total seven hundred. He was enthroned on the 1st of February 2009 implementing administrative reforms establishing Central Asian Metropolitan District reorganizing structure in Tajikistan Uzbekistan Kyrgyzstan Turkmenistan.
On the 15th of October 2018 Holy Synod severed full communion with Ecumenical Patriarchate responding to granting autocephaly to Ukrainian church. While Orthodox Church of Ukraine established on the 5th of January 2019, ROC claimed only legitimate jurisdiction remained its branch requiring name change under Ukrainian law ending 2018.