Short answers, pulled from the story.
The Khmer Empire began in 802 AD when Jayavarman II proclaimed himself chakravartin on Mount Mahendraparvata. This event marked the start of the Angkor period following his defeat of competing kings in Chenla.
Satellite imaging reveals that Greater Angkor Region had a population of approximately 700,000 to 900,000 at its height. This made it one of the most populous cities of the medieval world relying on an intricate system of reservoirs and canals for trade and irrigation.
Suryavarman II dedicated Angkor Wat to the god Vishnu over a period of 37 years starting in 1113. The construction demonstrates artistic and technical achievements through mastery of stone masonry.
Ponhea Yat abandoned Angkor as indefensible in 1431 after repeated sieges by the Ayutthaya Kingdom. Severe climatic changes including drought and floods damaged the water management system while religious shifts reduced the need for huge temples.
Zhou Daguan arrived in Angkor in August 1296 and wrote a detailed report known as The Customs of Cambodia describing ordinary houses with woven bamboo walls and thatched roofs on stilts. He noted that farmers lived near rice paddies while nobles resided in larger wooden shingle palaces.