Short answers, pulled from the story.
Jayavarman VII was king of the Khmer Empire from 1181 until his death around 1218. Historians generally regard him as the most powerful Khmer monarch because he drove out the Cham invaders who had sacked Angkor, expanded Khmer territory from Vientiane in the north to the Kra Isthmus in the south, and built 102 hospitals, 121 rest houses, and major temples including Bayon, Ta Prohm, and Preah Khan.
Jayavarman VII built 102 hospitals, 121 rest houses along raised highways spaced every 15 kilometers, reservoirs, and a series of major temples. His temple projects included Ta Prohm (dedicated to his mother in 1186), Preah Khan (for his father), the Bayon at the center of the new capital Angkor Thom, and Neak Pean, a small fountain temple set on an island in an artificial lake.
Jayavarman VII came to power by leading a Khmer army to oust the Cham invaders who had occupied Cambodia since 1177, when Champa King Jaya Indravarman IV sacked the capital Yasodharapura and killed the previous king. After the Cham forces were expelled in a campaign that included a naval battle, Jayavarman returned to the capital, resolved internal disputes, and was crowned king in 1181.
Jayavarman VII was a Mahayana Buddhist, the first Khmer king to be devoted to Buddhism (only one predecessor had been a Buddhist). His faith shaped his stated aim of alleviating his subjects' suffering and motivated his welfare programs. He placed stone Buddha images called Jayabuddhamahanatha in 23 towns across the empire, though Brahmans continued to hold roles at court during his reign.
After Jayavarman VII died around 1218, the throne eventually passed to Jayavarman VIII, a Shivaite ruler who systematically dismantled his predecessor's Buddhist legacy. Buddha images in the niches along the city walls were removed, the Buddha statue at the Bayon was taken down, and Buddha images in Angkor Thom were converted into linga.
Jayavarman VII first married Princess Jayarajadevi, and after her death he married her sister Indradevi; both women are credited with strengthening his devotion to Buddhism. Four sons are named in inscriptions: Suryakumara, Virakumara, Srindrakumara, and Tamalinda, who became a Buddhist monk. His crown prince Srindrakumaraputra died before him, and only Indravarman II ultimately inherited the throne.