Concealing qualification while applying for a job

Never do that. Such actions will always spoil your future. Hiding facts and providing wrong information is a very serious issue and if it is proved afterwards you may be in serious problems. You will lose your job and you may have to pay an additional penalty also.
One of my distinct relations did his PG and applied for a lecturer post. In that application, he claimed reservation under the SC category and submitted a wrong certificate. He got selected for the post and joined the job. But later on, the government received a complaint and they enquired and came to know that he is a brahmin and not an SC. Immediately he was removed from the post and he was asked to pay back all the money he received as salary and he was imprisoned for six months. This is a clear example of providing wrong information.
In your own interest, I suggest you don't do any such unwanted acts and get into complications.

No, I would not advise you to hide your qualification while filling up the application for the said post. You might be under the impression that it cannot harm you by suppressing your graduation qualification. However, you may not be aware of the people's motives living around you. The day someone complains against you that you possess a graduate degree and for the said post, the minimum qualification is undergraduate, you will be served a notice of violation of the model standing rules. Once the facts are verified, you will not only be terminated but the management may ask you for the entire amount to refund which they might have paid you by way of salaries and rewards during your service period. Apart from the termination, you may even be awarded jail for the suppression of the facts. In case, you are applying somewhere on the basis of graduation qualification, you cannot do so because of your bad record of imprisonment. Hence you should be careful while filling up an application form for the job where there should not be suppression of your earned qualifications to match your eligibility for the said post.

To put it bluntly, it is as wrong and deceitful to conceal information as it is to give dishonest details. Leave aside the fact that you are cheating the employer and yourself, it could have far-reaching issues that may jeopardize your future job prospects and career. You need to read the finer print that is mentioned in the terms and conditions of any job application. You may see the text that if you provide incorrect or wrong information, you are liable to "face dismissal and termination of your candidature/ service/contract and are also liable to face other penal action as per the law". This is the exact text I have seen often when submitting jobs here at our site. Also, keep in mind that your dishonesty could cause some eligible candidates to lose out on their candidature.

That said, note, however, that in some job recruitment notifications, it is mentioned that candidates with higher qualifications will be given preference. What I suggest is that you be honest. Since you indicate that you have already applied for the post if you are required to appear for an entrance test and/or interview you should inform them that you are a Graduate and had omitted to indicate it in your application. Be truthful and state that you were hoping to get the job. Do not take up the job with the concealed information. No matter that you do not get selected at all, You will not have to face the future ignominy of being dismissed from the job and having a black mark against your name, something that would be harmful in the future as you will then not get good references. More important, at least your conscience will be clear.

Hiding qualifications is an unlawful act as even in the eyes of law while signing any type of contract terms and conditions must adhere otherwise the employer has the right to claim all the damages if it comes to knowledge of him. Also doing a job with inappropriate qualifications will provide you short term gains but in long run, you would be in trouble as it is always said that truth always defeats falsehood. If this false information comes into the eyes of RBI then you would be expelled and charged. Also, they might give you some letters or prohibit you from being hired in another public sector or private sector job. Internally you will always hesitate and if we are speaking false or concealing something then we are always fearful and cant focus on our core tasks.