Does anyone know all the names that were used for Constantinople, in the original language?
What, legally, or colloquially? Are you including things like "Tsargrad", which is what the Russians called it, despite never actually controlling the place, or "Miklagarðr" (same thing, but for the Norse)? Cause, I mean, outside of "Byzantion", "Istanbul", and whatever Septimius Severus called it, I don't think the place really had a whole lot of legal, official names. Most of the names are colloquial ones.
The ones I can think of off the top of my head are Byzantion (Greek colony), Lygos (Thraco-Greek settlement), Augusta Severina/Augusta Antonina/whatever (Septimius), Roma Constantinopolitana/Nova Roma/Deutera Rome (colloquial, fourth century), Constantinopolis/Konstantinoupolis/Kostantiniyye/Kustantiniyyah (colloquial, Byzantine-era - Latin, Greek, Turkish, Arabic; I'm sure there's a Farsi version but I dunno Farsi), Istanbul/Islambol/Stamboul (colloquial, late-Byzantine and Ottoman, later official), Tsargrad (Russian), and Miklagarðr (Norse).
I know that Byzantion, Konstantinopolis, Konstantinoupoli, Nova Roma and Istanbul have all been used, but I don't know about other names.
Nova Roma was a colloquial expression for the city; more common would have been
Roma Constantinopolitana (insofar as anybody referred to it in Latin). There's no good evidence that it was actually renamed "Nova Roma".
Well, it started life as Byzantion, a Greek trading colony, which probably became Byzantium under Roman administration (but I'm sure Dachs can correct me there), and which of course was used by Emperor Constantine from which to rule the reunited Roman Empire. I think it only became Istanbul in 1918 or so.
Romans would have called it Byzantium, but they didn't go about legally renaming every city they controlled - insofar as one can talk about legal names of a city when the only real reference to most of them is coinage, and the Roman-controlled Greek East always coined in Greek. The people who lived there continued to call it Byzantion under Roman rule. I think Septimius Severus gave the city a Roman colonial name that basically nobody used after his death, but it wasn't "Byzantium" (something like Augusta Severina or Augusta Antonina IIRC).
Istanbul of course comes from the Greek expression "eis ten polis", which is "to the city" (or "in the city"), widely used from the Makedonian dynastic era onward; more often than not, Greeks would simply call it "the City" instead of referring to an actual name. Like with most Greek cities' names, the name was slightly rejiggered to make more sense in Turkish and then used by the Ottomans and other Turks.