Short answers, pulled from the story.
The Kushan Empire lasted from approximately 30 CE to approximately 375 CE. It fragmented in the 3rd century AD and was eventually overtaken by the Kidarites around 360 CE, with the final remnants destroyed by the end of the 5th century.
The Kushan Empire was founded by Kujula Kadphises, who united the Yuezhi tribal confederation by defeating the other four tribes and establishing himself as king. He then conquered the Kabul region and the kingdoms of Paktiya and Gandhara before dying at more than eighty years of age.
At its height, the Kushan Empire spanned much of present-day Afghanistan, Pakistan, India, Nepal, Tajikistan, and Uzbekistan. It extended from the Aral Sea region in the northwest through the Indus Valley and as far south as the Narmada river, and maintained influence east into the Tarim Basin.
The Kushans were major patrons of Buddhism and were directly responsible for spreading it to Central Asia and China through their control of the Silk Road. Emperor Kanishka convened a great Buddhist council in Kashmir and kept a direct road from Gandhara to China under Kushan control for more than a century. Kushan missionaries such as Lokaksema translated Hinayana and Mahayana scriptures in the Chinese capitals of Luoyang and Nanjing.
Kushan emperors practiced a range of faiths. The founder Kujula Kadphises followed the Shaivite sect of Hinduism, while also absorbing Greek and Iranian cultural elements. Vima Kadphises also embraced Shaivism. Kanishka the Great employed Zoroastrian elements in the imperial pantheon and was celebrated as a great Buddhist patron. Their coins depicted more than thirty gods from Iranian, Greek, and Indian traditions.
The Kushan Empire fragmented after the death of Vasudeva I around 225 CE. The western half was subjugated by the Persian Sasanian Empire under Shapur I, while the eastern half was absorbed by the Gupta Empire under Samudragupta in the mid-4th century. In 360, a Kidarite named Kidara overthrew the last Kushano-Sasanian rulers, and the remaining Kushan culture was wiped out by the Alchon Huns and later the Nezak Huns by the end of the 5th century.