Short answers, pulled from the story.
Li Yuan declared himself emperor on the 18th of June 618 following the murder of Emperor Yang by General Yuwen Huaji. This event marked the official founding of the Tang dynasty after decades of fragmentation under the collapsing Sui dynasty.
Wu Zetian acceded to the highest position of power in 690 after serving as a consort and making court decisions for her husband Emperor Gaozong since his stroke in 655. She proclaimed the Tianshou era of Wu Zhou on the 16th of October 690 before being forced to yield her position during a palace coup on the 20th of February 705.
The An Lushan rebellion destroyed Tang prosperity starting in 755 when half-Sogdian, half-Turkic commander An Lushan rebelled with an army exceeding one hundred thousand troops. The conflict ended in 763 but led to the rise of autonomous regional military governors called jiedushi who challenged central government power until the fall of the dynasty in 907.
Chang'an housed two million inhabitants making it the world's largest city at that time while containing diverse ethnicities including Persians Central Asians Japanese Koreans Vietnamese Tibetans Indians and many others. The capital featured fourteen main streets running east west and eleven main streets running north south forming one hundred eight rectangular wards.