Disabled brother

1. From where can I get the disability certificate. What is the procedure, how much time and money would be required.

doctor could have guided you.

2. If he gets the disability certificate, is he eligible to get my father's pension who expired 2 years back? If yes, what is the procedure for the same.

your query is vague. you have not intimated what pension your father was getting.

3. Can I get him enrolled as a dependent and avail medical insurance scheme from office?

your query is vague. you hve not told who is your employer / insurer.

If yes, what is the procedure?

ask your employer or insurer.  This forum cannot comment