And, concerning the russian general: Have you tried to use a general of an other nation with the russian cavalry formation (e.g. a french general because you know that this works with french cavalry)? Then you could check if it really is a missing animation or some other error.
If I add UnitKGen(FR) to Russian cavalry it works for them but then French cavalry won't form up. I can't even plop a French cavalry formation in the editor, only individual cavalrymen. The same unit with the same nation designation (FR for example) can not be used by more than one nation at a time.