Short answers, pulled from the story.
Arsaces I led the Parni tribe to seize control of Parthia in 247 BC, marking the official start of the Arsacid era. He initially served as chieftain within the Dahae confederation before exploiting chaos during the Third Syrian War between 246 and 241 BC.
Marcus Licinius Crassus invaded Parthia in 53 BC with seven Roman legions but was defeated by Surena's force of 1,000 cataphracts and 9,000 horse archers. Approximately 20,000 Romans died during the battle while another 10,000 were captured and 10,000 escaped westward into Armenia.
Zhang Qian traveled into Central Asia during Emperor Wu of Han's reign spanning 141 to 87 BC and opened official trade relations with Mithridates II's court in 121 BC. The Han embassy established commercial exchanges via the Silk Road importing silk which became the most expensive luxury good brought westward by Roman merchants.
The script does not specify the total number of kings who ruled the Parthian Empire from 247 BC until 224 AD. It mentions specific rulers such as Arsaces I, Mithridates I, Orodes II, Phraates IV, Vologases I, and others but provides no aggregate count.
Hecatompylos served as the first capital before Mithridates established royal residences at Seleucia, Ecbatana, Ctesiphon, and his newly founded city Mithradatkert. Ctesiphon may not have become the official capital until later under Gotarzes I but remained the site of coronations.