That was money returned to Iranian citizens from individual private bank accounts frozen by Carter in 1979.
Sponsor terrorism? Such as in Syria or Iraq against ISIL?
In both arenas, it is Iran that has the most foreign troops on the ground, not Russia, and certainly not the US. Iraqi Shiite militias that the US backs are basically ethnic Iranians, and Iran has done far more to arm and train them more than we have. Same goes for Kurds, also an Iranic ethnicity. "These freedom fighters" (Reagan) that America supports are, yes, sponsored by Iran. As with Bosnia and Kosovo, Iran does the dirty work that the US cannot openly do, which is why ZERO effort has ever been made to halt it.
Compare that to what's going on in Yemen, where the US backs the Saudi puppet regime and Iran backs the oppressed Houthis, and the US response to the latter.
You're also right on it's not always Russia.... Perhaps Trump should stop prostrating himself before Putin, his center of his universe.