Short answers, pulled from the story.
Kievan Rus' was the first East Slavic state, encompassing East Slavic, Norse, and Finnic peoples across Eastern Europe from the late 9th to the mid-13th century. At its greatest extent in the mid-11th century, it stretched from the White Sea in the north to the Black Sea in the south. It was ruled by the Rurik dynasty, founded by the Varangian prince Rurik.
The term Kievan Rus' was coined by Russian historians in the 19th century to describe the period when Kiev was the dominant center of the state. The underlying name Rus' is likely derived from an Old Norse term for 'men who row', connected to the Swedish coastal district of Roden, and is related to the Finnish word Ruotsi and Estonian word Rootsi, both meaning Sweden. The English version first appeared in the 1913 translation of Vasily Klyuchevsky's history of Russia.
According to the Primary Chronicle, the Varangian prince Rurik established himself in Novgorod around 862. After Rurik's death around 879, his kinsman Oleg served as regent, capturing Kiev in 882 and making it the capital. Oleg consolidated control over surrounding tribes, cutting off their tribute to the Khazars and redirecting it to Kiev, establishing the foundations of the state.
Vladimir the Great was baptised around 987 and ordered the population of Kiev baptised in August 988. His choice of Eastern Christianity was influenced by the Byzantine connection, including his marriage to Princess Anna, sister of Byzantine emperor Basil II. The strongest resistance to Christianization came from northern towns including Novgorod, Suzdal, and Belozersk.
The Russkaya Pravda was the first written legal code of Kievan Rus'. It was assembled and issued by the sons of Yaroslav the Wise shortly after his death. The code confined punishments largely to fines and generally avoided capital punishment, and it accorded certain rights to women, including property and inheritance rights.
Kievan Rus' fell due to a combination of internal fragmentation and external pressures. After Yaroslav the Wise's death, succession disputes broke the state into rival principalities. The decline of the Byzantine Empire eroded the Dnieper trade route that was the basis of Kievan wealth. The Fourth Crusade's sack of Constantinople in 1204 made that route marginal. The Mongol invasion of the late 1230s delivered the final blow, with the siege of Kiev in 1240 marking the formal end of the state.