Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Degree U
POLYNOMSURFACE_UDEGREE
Parameter: Degree V
POLYNOMSURFACE_VDEGREE
Parameter: Points U
POLYNOMSURFACE_UPOINTCOUNT
Parameter: Points V
POLYNOMSURFACE_VPOINTCOUNT
Parameter: Closed U
POLYNOMSURFACE_UCLOSED
Parameter: Closed V
POLYNOMSURFACE_VCLOSED