How aware were the medieval Byzantines of their Roman Republican predecessors? If you threw around names like Scipio Africanus, Marius, and Sulla, would literate middle-class merchants be able to tell you about their deeds?

Probably not.

A few exceptionally well-educated Byzantines could have told you something about the Roman Republic. In his Bibliotheca, for example, Photius mentions reading Appian's Roman History, and briefly summarizes the end of the Republic:

"[Appian's] account of the civil wars contains first the war between Marius and Sulla, then that between Pompey and Julius Caesar, after their rivalry took the form of violent hostilities, until fortune favored Caesar and Pompey was defeated and put to flight." (57)

But most Byzantines, even those who were literate, probably knew a great deal less. The description of Constantinople known as the Parastaseis syntomoi chronikai, which probably dates to the eighth century, provides our best look at common (literate) views of the city's history and artistic heritage at that time. The author of the Parastaseis claims (possibly falsely) to have read several late antique historians; but his historical references are almost incredibly ill-informed, and seem to reflect general ignorance about (and indifference to) Roman history before Constantine.

So, while scholars like Photius could still access texts about the Roman Republic, Joe Byzantine likely knew little beyond the fact that it had existed.