1) "Well there is no Limit for the this under company law, but as per the SEBI (SAT) Regulations, there are certain trigger points first point is 5%, and as soon as you reach the holding to the level of 5% of the total shares of the company then thereafter with every change of 2% also a person needs to give a disclosure.
Therefore the upper celling limit is 5%, i.e. a retail investor can acquire something upto bellow 5%, from the secondary market.
But if the subscription is made in the IPO then the current limit is expressed in monetary terms and it is 2 Lacs per investor."
Quoted from Quora:
2) According to Securities and Exchange Board of India a block deal is a single transaction of a minimum quantity of five lakh shares or a minimum value of Rs 5 crore and is done between two parties through a separate window of the stock exchange that is open for only 35 minutes in the beginning of the trading hours.