is interview possible for that post (Reserved for the physically handicapped person) where only candidate' form found eligible.

What is the present issue bothering you?

it is left to the discretion of the employer to decide on recruitment because there is no other applicant for the post, it is not mandatory to appoint that candidate that alone applied.

A good employer can decide the suitability of employees by going through biodata or some other way.  A candidate may be eligible for the post, but it is not mandatory that he should alone be selected as the candidate may not deserve such post.

In my understanding, the lone applicant need not be appointed just as a matter of course; an interview or the required screening need to be conducted before offering appointing. However, it would be a travesty of justice if the lone applicant is denied appointment just because there is no other applicant. The judicious procedure would be to ascertain the suitability of the lone applicant through the prescribed procedure and offer him/her appointment, if found suitable.

You are very well qualified and eligible for the post.

However, there might be some specific reason, where you are not suitable for the appointment and non-calling you.

As already suggested, you may take up matter through a Writ petition. It is often that public authorities are reluctant in taking up the responsibility of correcting unintelligent procedures; a direction from the High Court is the best remedy.