the first pic, this should pop out and there should be a set of bearings in a cage behind this. i think this is the part that the sprocket fits on to and moves the clutch in or out to engage the coaster brake. the 2nd pic should have a smooth drum like look to it where the brake pads fit in so not sure what the splines are. but the main hub area on the rear is i should imagine only done in the factory and not to be replaced.
not sure about the fronts as you can replace the bearing cups on alloy hub skyways, so you may be able to on these. but make sure you get replacement cups first and they will need a big hammer or some kind of press to remove
i'm sure they only came in suntour,shimano and bendix coaster rear
