Ancestral property

Our Grand father purchased some 2.30 Acress of Agriculture Lands in 1901. He passed away without made any partition or will or any other arrangements among his two Sons. Hence , In the year 1950 my father and his younger brother filed a partition suit in a civil court and got a partition decree for the properties above mentioned along with some other lands and house properties. Among our father's share schedule, in 1961 our father borrowed about Rs.5000.from a money lender, by pledging the above mentioned 2.30 Acress of Agriculture Lands, in that mortgage deed also we three signed. Subsequently in 1978 we repaid the loan and the discharge document also executed on the name of our three. Further that, In 1984 Our father sold some other lands to some body along with me and my brother. We three signed in that Sale document. In 2023 October we have downloaded a chitta of the said land.it shows some other person's name. On verification of the Encumbrance certificate , a memo entry showing that,our father was sold the said 2.30 Acress land to some body in the year 1980 at Chennai Sub registrar office. .We obtained a Certified copy of the document from the above SRO. From that, we came to know that sale deed may be a fake one, since the land situated at Dharmapuri , our father lived at Dharmapuri with us, and the purchaser's address also Dharmapuri , but the document was executed at Chennai SRO, that too with out my self and my brother names and Signatures. The 2.30 Acress of lands were in our possession till date. Untill September 2023, the Chitta was in our Father's name, and there is no entries in the Encumbrance certificate. Based on the new chitta and EC, the persons tried to sell out our property. We filed a suit in the local Civil court, for interim injunction. Now our questions are :- 1.Whether the said sale deed is valid one ? 2. If our father's signature is forged how can we take next step ? 3.If suppose our father originally signed in that document , how much land he can sell ? 4.How can we protect our title of our shares in the above 2.30 Acress ancestral property?