What is the age of superannuation according to it. ??
If its 58; then the employee has to be necessarily superannuated at 58. Date of Birth as given in the Employment Form is sufficient and adequate - no further proof of Date of Birth is required, once it is accepted.
Proof of Date of birth is only required if the employee want to contest his age.
The case of retention for 3 years, is up to the management; and the person can be retained as consultant or any other appropriate designation; not being that of a regular employee.
In addition to Mr. Raj Kumar, I would like to add the following
What is his level of employment. If he is in workman level and he is fit to perform his duties properly without any health issues, then you can keep him upto the age of 60 years. But you can consider as per your company policy and if the company policy is not permitting then you can appoint him in the same position and on re-employment basis with consolidated salary / honorarium, in which you need not to deduct anything including PF.