Short answers, pulled from the story.
Li Longji was born in 685 and his mother Consort Dou was murdered by Empress Dowager Wu Zetian in 693. The bodies of his mother and aunt Crown Princess Liu were never recovered leaving him and his brothers in constant fear within the palace walls.
The Kaiyuan era was a period of unprecedented prosperity and stability that defined the Tang dynasty's golden age during the first three decades of his reign. This era ended in 734 when he allowed Li Linfu to rise to the position of chancellor leading to the collapse of the Tang dynasty.
Yang Yuhuan was the wife of his son Li Mao whom Emperor Xuanzong took into the palace as his senior-ranking concubine known as Yang Guifei in 745. Her rise to power was unprecedented as she was treated like an empress and her family members were granted immense wealth and influence.
The general An Lushan rebelled against Emperor Xuanzong of Tang in 755 declaring himself emperor of a new state of Yan. The rebellion spread quickly capturing the eastern capital of Luoyang and then the imperial capital of Chang'an six months later forcing the emperor to flee to Sichuan.
Emperor Xuanzong of Tang died in 762 depressed and ill after a life that had gone from the heights of power to the depths of despair. His legacy was one of tragedy as his early successes were overshadowed by his later mistakes which led to the decline of the Tang dynasty and the eventual collapse of the empire.