I don't do history but I it's one of my... let's say hobbies... History is like a giant set of dominoes with events causing other events and so on. Hence, having a good understanding of events that have lead to the particular event (which ever revolution) will give you an advantage. BUT, from what I can see, since there's no UNits 1 and 2 revs, you won't be behind in terms of knowledge by that far. (eg: Units 1&2 ancient and aus history is irrelavent, Global empires might help with the whole poltical atmosphere that lead to french rev, 20th century will help with Russian rev). Skills might be a bit hard with the whole "history analysis vibe" and essays or whatever they do. But I think you'll be fine if you put in the effort.
Do take my advice with a grain of salt since I'm no where near qualified to give advice.