Sale deed without mutation is a valid in revenue act yes or

Hello ,respected all I am from Hyderabad my friend has 12 acres in vikarabad district previously ranga reddy dist.The land belongs to anscestral property .Not earn by his father,his grand father sold that 12 acres property to some X. Without giving any information to his sons.Some Y has purchased land and registered sale deed in the name of some society. Here Y Did a huge mistake in documents that Y Purchased total 25 acres at the same time But here if we absorb clearly in sale deed 12 acres belongs to some P mandal another 13 acres belongs to some Q mandal but at the time of sale deed in 2001 registar made total 25 acres land in P manda,...l for that reason mutation of land failed.After some days my friends grand father has died .Legal heirs of that deceased has applied for succession ....succession got sucssesed .After getting succession the grand sons once again sold above said 12 acres to some R From 2002 to up to date revenue records showing the land in the name of R. Now the problem raised is the person who got the land in 2001 from my friends grand father I,e ( who has just sale deed ) has occupied position from last one year My question is 1) is the registration sale deed done with different revenue mandal is valid or not 2) Only sale deed without mutation or without entering his name in revenue records is a valid owner or not?