Game haven't been updated in 4 years so I don't really see the point of the necro.
Kagura's version and DLsite version are different number since each start at 1.0 at the release, and Kagura always use the latest version provided by the dev (which unless still in work should be the last released on dlsite).
An no, even if the mother is in the character customisation, there only two scenes with her where clothes doesn't matter (nude in one, event clothing in the other).
So yeah, probably one of the usual massive thing the dev wanted at one point to use but never got to add / finish....