Whether I need to give bank account details at the time of account opening?
It is for your own protection. The bank account number will be mentioned on the interest or dividend warrant, so that such warrant cannot be encashed by any one else. Further, cash corporate benefits such as dividend, interest will be directly credited to your account through the ECS (Electronic Clearing Service) facility, wherever available, by the company. This would reduce the paper work at your end for depositing the cheque, loss of cheques in transit etc.

Do I need to maintain a minimum balance in my account?
No you are required to maintain any minimum balance of securities in your DP account. You can hold even 1 share of a company.

Whether I can change the details of my bank account?
Yes. Since in the depository system monetary benefits on the security balances are paid as per the bank account details provided by you at the time of account opening, you must ensure that any subsequent change in bank account details is informed to your DP immediately.

Can I close my demat account with one DP and transfer all securities to another account with another DP?

Yes you can. You can submit account closure request to your DP in the prescribed form. The DP will transfer all the securities lying in the account, as per the instruction, and close the demat account.

Whether I can freeze or lock my account?
You can freeze or lock your account for any given period of time, if so desired. Accounts can be frozen for debits (preventing transfer of securities out of accounts) or for credits (preventing any movements of securities into accounts) or for both.