Yes, its a breather hose, the idea being, if you drive through high water it can get into the differential and its oil through the breather port, so a hose runs extends the opening of the breather much higher to avoid that.
No vacuum lines to the differentials, I don't think there is any aftermarket parts for the Commander that use vacuum either. Only the QDII has locking differentials and that is controlled electrically, NOT with vacuum.
The broken plastic piece on the end, NOT sure if there is a pressure valve in it, filter or maybe just a redirect vent to avoid sucking dirt and moisture. Eitherway, the original cap appears to have something smarter than a simple opening at the end of the tube. Might be worth it to visit a dealer and get an actual replacement part for the end of the tube, instead of finding some plastic piece in a hardware store.
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