How will I know whether I am eligible for corporate actions announced by the company or not?

To understand this, you need to understand two concepts: 

Record Date: This date is announced by the company, and you must have the stocks credited to your Demat account on or before the record date to qualify for corporate action. 

Ex-Dividend Date: Stocks take T+1 (Trading+1) day to be delivered to your Demat account. Ex-Dividend date is the day by which you must make the transaction so that the shares are credited to your account by the record date. Any buy transaction made after the ex-dividend date will not be eligible for corporate actions. 

Note: Corporate action benefits are directly credited to the eligible shareholders by the registrar and the broker does not play any role in the same.