Gina legal heirs can file suit to direct IOC and dealer to vacate land 

2) seek orders that lease agreement is not valid as he was owner of 0.52 acres and has not signed any such agreement 

3) engage a local lawyer 

Based on the information provided, here are answers to your questions regarding the dispute on the legal agreement with IOC:

1. 
   Will this lease agreement be valid? The validity of the lease agreement depends on whether Vijay had the authority and consent of all the co-owners of the land to enter into such an agreement with IOC. If Vijay had obtained the power of attorney from Govind and Raj and also informed Guna about the lease agreement, then the lease agreement may be valid. However, if Vijay had acted without the consent or knowledge of Guna or you, then the lease agreement may be invalid and voidable. You can challenge the validity of the lease agreement in court on the grounds of fraud, misrepresentation, or breach of trust by Vijay.
2. 
   If the agreement is not valid, can I ask IOC to vacate the petrol pump? If the agreement is not valid, you can ask IOC to vacate the petrol pump by sending them a legal notice or filing a suit for injunction and eviction in court. However, you may face difficulties in doing so, as IOC may claim that they are bona fide lessees who have paid rent and invested in the property in good faith. IOC may also claim that they are not aware of any dispute or defect in Vijay's title or authority to lease the land. You may have to prove that IOC had knowledge or reason to believe that Vijay was not authorized to lease the land without your consent.
3. 
   If the agreement is not valid, can I ask the dealer to vacate the petrol pump? If the agreement is not valid, you can also ask the dealer to vacate the petrol pump by sending them a legal notice or filing a suit for injunction and eviction in court. Similar to IOC, the dealer may claim to be a sub-lessee or licensee of IOC who has acted in good faith. You may need to prove that the dealer had knowledge or reason to believe that Vijay or IOC lacked the authority to lease the land without your consent.
4. 
   How to proceed with Vijay, who entered into a lease agreement with IOC without Guna? You can proceed against Vijay by sending him a legal notice or filing a suit for declaration and cancellation of the lease agreement in court. You can also claim damages for breach of trust and loss of income from Vijay. Seeking an injunction to restrain Vijay from interfering with your possession and enjoyment of your share of the land is an option as well.
5. 
   How to proceed further without going to court, like sending a letter of my own to IOC, the dealer, and Vijay? You can attempt to resolve the matter amicably by sending a letter explaining your situation and requesting them to vacate the petrol pump within a reasonable time. Offering some compensation for their investment and inconvenience might facilitate a resolution. However, if they refuse to cooperate or negotiate, you may need to seek legal assistance and pursue legal action.
6. 
   How to proceed further with a lawyer/court? To proceed further with a lawyer and court, you should consider hiring a lawyer experienced in property law and lease agreements. Consult with the lawyer to get advice on the best course of action. Discuss legal fees, expected timelines, and the likelihood of success for your case. Be prepared to provide all relevant documents and evidence to support your case, including Guna's registered document, the lease agreement between Vijay and IOC, the RTI reply from IOC, and any other pertinent records. Maintain communication with your lawyer to stay informed about case progress and outcomes.

legal heirs of Guna have to take legal proceedings  to direct IOC and dealer to vacate property 

Yes if agreement is not legal then you can. You need to send a notice and file a proceeding in civil court against him

1. The lease agreement entered between IOC and Vijay is valid to the etent of Vijay's share at the time of entering into the lease agreement, however it appears that Guna has not raise any objection or had claimed a share out of the rental amount all through his lifetime after purchasing the 1/6th common share in the property.  However  it cannot be said that the lease agreement is invalid.

2. Since Guna's share in the property has not been divided yet, the legal heirs of Guna can file a suit for partition and for separate possession of their share in the property. After that the legal heirs of deceased Guna can either continue the leas agreement by entering into a fresh lease agreement with IOC or can issue an eviction notice followed by an  eviction suit.

3. The lease agreement is valid, however without identifying your share in the proeprty you cannot ask the IOC to vacate becasue there is a valid registered lease agreement and that too it is effective for over 23 years till this date.

4. Suit for partition, read the answer given in point 2 above.

5. You cannot solve the problem without involving legal steps.

6. You can proceed as suggested above

You were advised to file a suit for partition after issuing a notice for partition and separate possession of yor share in the property, if there is no possibility for an amicable partition then it would be better that you appraoch court instead of wasting time with the reluctant people

Sir/Madam,

It is suggested to read the lease agreement carefully becasue when Guna died, the lease deed might be enforeceable throguh his legal heirs/successors/assigns etc. If the same is not valid then you may proceed for cancellation of the said deed and vacation accordingly.  

Greetings of the Day,

I have read your issue but find that there are some facts which need to be clarified. You can approach on either nine two one two one two four five eight five or seven zero four two eight three three six eight six for personal approach.

We Hope that a personal consultation would be fruitful to the issue and it would be better for you to talk to someone directly.

Best Regards

SPS Law Chambers
New Delhi.