Short answers, pulled from the story.
The land known as Dacia stretched from the Black Sea to the river Tisza and extended from the Middle Danube to the littoral between Apollonia and Pontic Olbia. The Carpathian Mountains sat in the middle of this vast region while ancient Greek writers like Herodotus first mentioned these people in Histories Book IV XCIII.
Julius Caesar was a contemporary of King Burebista who governed Geto-Dacian tribes until 44 BC. In 53 BC Caesar stated that Dacian territory lay on the eastern border of the Hercynian Forest before suppressing indigenous minting by four major tribal groups.
King Decebalus ruled the Dacians between AD 87 and 106 with frontiers marked by the Tisa River to the west. He committed suicide to avoid capture after Trajan razed the capital Sarmizegethusa to the ground ending with annexation of most of Dacia.
Emperor Aurelian reorganized the later province Dacia Aureliana inside former Moesia Superior between AD 271 and 275. It was divided into Dacia Ripensis as military province and Dacia Mediterranea as civil province while Roman citizens were resettled to interior of Moesia under Diocletian around AD 296.
The Huns destroyed Drobeta and Sucidava in 440s but forts were restored under Justinian I between 527 and 565. Slavic people arrived while Lombards abandoned country allowing Avars to dominate region for 230 years until Charlemagne destroyed kingdom in 791.