Short answers, pulled from the story.
The Sasanian Empire began in the year 224 when Ardashir I defeated and killed the Parthian king Artabanus IV. Ardashir I, a local governor from the province of Pars, founded the empire and was crowned Shahanshah at Ctesiphon that same year.
The Roman Emperor Valerian was captured alive by the Sasanian King Shapur I in the year 260 and remained a prisoner for the rest of his life. Shapur I celebrated this victory by carving monumental rock reliefs at Naqsh-e Rostam and Bishapur depicting the emperor kneeling before him.
Khosrow I, also known as Anushirvan or the Immortal Soul, ruled from 531 to 579 and implemented a rational system of taxation based on a survey of landed possessions. He created a new military force known as the dehqans and rebuilt canals and restocked farms to strengthen the empire.
The Sasanian Empire collapsed in just five years after the death of Khosrow II, ending with the assassination of Yazdegerd III by a miller in Merv in late 651. Yazdegerd III was a grandson of Khosrow I who ascended to the throne in 632 as a boy.
The Sasanian Empire's cultural and administrative legacy was absorbed into the nascent Islamic civilization, with the Caliphs adopting the old Sassanid land tax known as kharaj. The centralized bureaucracy and provincial governance of the Sasanian Empire influenced the structure of the Islamic caliphates and the Samanid dynasty sought to revive Sasanid traditions.