Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Object
OSHAPE_OBJECTParameter: Bounding Radius
OSHAPE_RADIUSParameter: Render Instance
OSHAPE_RENDERINSTANCEParameter: On
IN_OSHAPE_ONParameter: Animation Time
IN_OSHAPE_ATIME