Difference between release order and acceptance of resignation

Show the appointment letter to a local prudent lawyer for proper appreciation of terms and conditions envisaged / accepted as the  facts posted by you are impractical and unbelievable .

Thanks 

He is my brother. As advised,checking with Maharashtra based labour law lawyer.

If the previous company's terms say that you have to serve 50 days which was accepted by you at the time of joining then you cannot agitate that now, you may have to request the new company to defer your joining date accordingly.

In my understanding, the acceptance of resignation amounts to release, unless such acceptance itself in conditional and there has been no cessation of employer-employee relation. 

There are no laws regarding leaving one private company and joining another private company. The only requirement would be that you should not be simultaneously employed full-time in two companies and drawing salary from both the companies. If your resignation has been accepted by the first company and they have stopped paying you salary, you can very well accept employment in the second company without waiting for release by the first company.

Even when you leave a Government employment and join private employment often if the superior officer in Government does not like your taking up better employment he will dilly-dally your resignation. On such occasions the private company would not bother about your previous employment. The only thing is that you should not be cheating anybody. This is still a free democratic country.

Joining another company with similar business can be restricted for "some" time by employer, which may or may not be acceptable to employee at the time.

However, once resignation is accepted the employer cannot impose any such restriction.