Explanation:

- Option 1: Bank rate is indeed the rate at which a central bank lends to commercial banks. This helps manage liquidity and control inflation.

- Option 2: It's true that bank rates and interest rates differ. The bank rate influences the interest rates that commercial banks charge to borrowers.

- Option 3: The bank rate can be considered the discount rate of the central bank. It’s the rate applied to loans or advances given to commercial banks, often through rediscounting bills.

- Option 4: This is correct since all the above statements are true.