Short answers, pulled from the story.
The Astrakhan Khanate existed from 1466 until 1556. Mahmud bin Küchük sent a letter to the sultan in 1466 claiming the area as his patrimony, marking the first clear assertion of independence from the Golden Horde.
Historians debate whether Mahmud or his son Qasim I actually founded the entity. Mahmud established his base around Astrakhan while Ahmed controlled other territories after the death of Golden Horde ruler Küchük Muhammad in 1459.
Most land now belongs to Astrakhan Oblast and steppeland on the right bank of Volga in present-day Kalmykia. The capital city Xacitarxan stood twelve kilometers north of modern Astrakhan when conquered before authorities moved the settlement twelve kilometers south to its present location in 1558.
Sunni Islam functioned as the state religion throughout the khanate's existence. After Russian conquest in 1556, Sunni Islam largely gave way to Russian Orthodox Christianity, though the region remains home to a Sunni Muslim minority today.
Russia occupied Astrakhan in 1556 proceeding to destroy the largest slave market on the Volga. In 1558 authorities moved the settlement twelve kilometers south to its present location from where it had stood twelve kilometers north at the time of conquest.