Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Subdivision X
BEZIEROBJECT_SUBRX
Parameter: Subdivision Y
BEZIEROBJECT_SUBRY
Parameter: Grid Points X
BEZIEROBJECT_SUBX
Parameter: Grid Points Y
BEZIEROBJECT_SUBY
Parameter: Closed X
BEZIEROBJECT_CLOSEX
Parameter: Closed Y
BEZIEROBJECT_CLOSEY