Short answers, pulled from the story.
The Khanate of Kazan was founded in 1437 or 1438 by Ulugh Muhammad, who assumed the title of khan and seized the throne with support from local nobility. His son Maxmud is believed to have completed the formal transfer of power from the older Bolgar dynasty in 1445.
Ivan the Terrible besieged Kazan beginning in August 1552, operating from the fortress-island of Sviyazhsk. On the 3rd of October 1552, after two months of siege and the destruction of the citadel walls, Russian forces entered the city, killing most defenders and slaughtering the population.
The khanate was multiethnic, encompassing Kazan Tatars, Chuvash, Mari, Mordvins, Udmurts, Bashkirs, and Mishar Tatars, among others. Russian sources record at least five languages in use, including Old Tatar as the written state language, Chuvash, Mari, Mordvin, and Bashkir.
There were fifteen reigning khans over the khanate's 115-year history, though the throne changed hands nineteen times in total because some khans ruled more than once. The khan was often elected from among Genghizide candidates by the nobility and sometimes by citizens themselves.
Söyembikä was the mother of the three-year-old khan Ütämeşgäräy and served as regent after Safa Giray died in 1549. She was the de facto ruler of the khanate during that period, though the administration of the ulan Qoşçaq gained substantial independent authority under her regency. She was ultimately sent to a Moscow prison in 1551 along with her son.
After 1552, Tatars were forcibly resettled away from rivers, roads, and the city of Kazan. Orthodox bishops including Germogen carried out forced baptisms. The administration known as the Kazan Palace's Office oversaw the forced Russification and Christianization of Tatars and other peoples, a process that continued until at least 1708 when the Kazan Governorate replaced the earlier administrative term Tsardom of Kazan.