Russia is practically turning a blind eye to Turkey and Yank occupation of Syria. Then why not Iran?
AFAIK Russia has not told Iran what it can or cannot do in Syria and I don't think they will start now.
Israel might complain to Russia.... they like to complain about all sorts of things, but I doubt Russia would help Israel against Iran, but of course Israel would start attacking Iranian troops even more if they started doing anything like this, which means they would need to move serious air defence capability with them.
I would think Russia would like to see the US forces kicked out of Syria, and I don't think they would mind if Syria got its land in the Golan heights back either.