Short answers, pulled from the story.
Konstantin Ustinovich Chernenko was a Soviet politician who served as the de jure leader of the Soviet Union from the 13th of February 1984 until his death on the 10th of March 1985, a tenure of just over thirteen months. He held the posts of General Secretary of the CPSU Central Committee and Chairman of the Presidium of the Supreme Soviet during that period.
Chernenko rose through the Communist Party primarily through his long association with Leonid Brezhnev, whom he first met while heading the propaganda department in the Moldavian Soviet Socialist Republic in 1948. He followed Brezhnev to Moscow in 1956, became his chief of staff in 1960, and by 1978 was a full member of the Politburo, second only to the General Secretary in the Party hierarchy.
Chernenko had emphysema and right-sided heart failure long before taking office, and in 1983 he was absent from his duties for three months due to bronchitis, pleurisy, and pneumonia. During his leadership he governed partly from the Central Clinical Hospital in Moscow, was driven by wheelchair because he could not walk the corridors, and by late 1984 the Politburo was using a facsimile of his signature on all letters. He died on the 10th of March 1985 of chronic emphysema, heart failure, and liver cirrhosis at age 73.
On the 8th of May 1984, the USSR under Chernenko announced it would not participate in the Los Angeles Summer Olympics, citing security concerns and what it called anti-Soviet hysteria in the United States. The move was widely seen as retaliation for the U.S.-led boycott of the 1980 Moscow Games. Fourteen Eastern Bloc nations joined the Soviet boycott, including Cuba but not Romania, and the boycotting countries organised their own Friendship Games that summer.
Because of Chernenko's deteriorating health and limited support within the Party, real power was effectively shared in an unofficial triumvirate. Defense Minister Dmitry Ustinov and Foreign Minister Andrei Gromyko governed alongside him, and historian Vladislav M. Zubok noted that Ustinov and Gromyko retained a virtual monopoly in Soviet military and foreign affairs.
Chernenko is buried in the Kremlin Wall Necropolis, in one of the twelve individual tombs located between the Lenin Mausoleum and the Kremlin Wall. He is the last person to have been interred there.