Rishi’s point above seems to be logical & possibly explains why some companies do not get traded nor have volumes, altho they r listed. If listed companies default on trading regulations/norms such as timely payment of fees etc to the exchng, the exchange may take a call not to allow trading - in which case, public announcements are made from time to time for info of general investors/traders.
Reg the two companies cited here by Nithyanand, I have no info though.
Reg cap on promoter holding - link may be of use to folks on this thread.
Hope this helps.