I would like to know the following:

1. How Indian IT companies do a background check?
2. Do McAfee do background verification of employees even if it is not mentioned in appointment letter?
3. Suppose a candidate has worked with more than two companies previously and the new company (say McAfee) asked "Relieving letter only from previous employer". Then how the new company will verify all the previous employments? 4. In the above case, do the new company ask the previous employer for the documents which the candidate submitted in the time of joining the previous company?