From the facts stated by you, your case appears to involve wrongful mutation/revenue entry and possible illegal occupation of assigned agricultural land originally granted to your grandmother in relation to your deceased uncle who died in military service.
The most important point to understand is that mere online revenue entries or pattadar entries do not automatically confer valid title if the original assignment and succession rights are legally in your favour. At the same time, since the other persons are presently shown in online records and are stated to be in cultivation, immediate legal action is necessary because delay may complicate matters further.
Since you possess the original assignment and title-related documents, those documents will be extremely important. You should immediately collect and preserve: the original assignment order/grant proceedings of 1976, old pahani/adangal records, 1-B register extracts, ROR records, tax receipts, resurvey notices, death certificates of your grandmother, father and uncle, legal heir certificates, and any prior cultivation or possession records.
You should also immediately apply for certified copies of: current online revenue entries, mutation proceedings, pattadar passbooks issued to the other persons, DKT/assignment records if any, and the basis on which their names were entered.
If the Tahsildar has not passed orders on your representation even after three months, you should not remain passive. You may proceed with: an appeal/revision before the Revenue Divisional Officer (RDO) or competent revenue appellate authority, and simultaneously seek certified copies through RTI applications.
If pattas have been granted to third parties without notice to legal heirs and without cancellation of the original assignment rights, such proceedings may be challengeable.
However, since possession is presently with the other persons and there appears to be a dispute regarding title and cultivation, revenue authorities alone may not fully resolve the issue. In many such cases, parties ultimately need to file: a civil suit for declaration of title, recovery of possession, cancellation of illegal entries/mutations, and permanent injunction.
You should also carefully verify whether the original assigned land carried any restrictions on transfer or succession under Andhra Pradesh assigned lands laws, because the nature of assignment conditions can affect inheritance rights and validity of subsequent pattas.
If the land was assigned to your grandmother for the benefit of the deceased soldier’s family and the assignment remained within the legal heirs, your succession claim may still survive. But if government authorities later treated the land as abandoned, resumed, or eligible for reassignment due to long non-cultivation or absence, that issue may also arise and will need factual examination.
The fact that the persons whose names are entered did not attend the resurvey proceedings may help your case, particularly if no proper notice or adjudication occurred before mutation.
At this stage, your immediate next steps should be: obtain all certified revenue records and mutation proceedings, file RTI applications seeking the basis of current entries and pattas, pursue appeal/revision before higher revenue authorities, and consult a local civil lawyer to prepare for declaratory and possession proceedings if revenue remedies fail.
You should also avoid further delay because prolonged possession by third parties may later give rise to adverse possession or equity-related defences.
In conclusion, the online entries and pattas in favour of third parties are not necessarily final if they were obtained illegally or without proper process. Since you possess original documents and claim legal heirship, you appear to have an arguable case to challenge the revenue entries and seek restoration of title and possession, but prompt legal proceedings and collection of certified records are now essential.