Probate of a will in Bihar

There is a plot in Bihar (6000 sq. ft., registered in my grandmother's name in 1963, self acquired). My Grandfather passed away in 1990 and my Grandmother passed away in 2013. My father has 2 brothers (one elder and one younger ) however, my father passed away in 2017, he had a job and we hardly lived in our hometown and all the papers of all the joint properties (including that plot) we had, are in my elder uncle's possession. My Aunts (my father's sisters) had mentioned on a couple of occasions that out of that 6000 sq.ft. plot, 4000 sq. ft was registered in my name, most likely in 1986 when my Grandfather was still alive and I was a MINOR, since I was very dear to my grandfather. My elder uncle never shared any paper of the property and after 6 years of my grandmother passing away, in 2020 (she passed away in 2013), it was brought to everyone's notice that My grandmother had made a WILL in 1989 (when my grandfather was also alive, BUT I WAS A MINOR). IT IS A REGISTERED WILL. According to the WILL: 3000 sq. ft has been given to me (instead of 4000 sq. ft) and 3000 sq. ft has been given to my elder uncle's 2 sons (my elder uncle has 2 sons only, and I am the only son). I have a serious doubt about the Genuinity of the will, because my elder uncle is known for his cheating nature as he sold out other joint properties (we had our share in those properties but since we were not living in our hometown, hence he took advantage of it) after my grandfather passed away. My Younger uncle has not been given any share in that plot and now he is forcing me to give him an equal share. Now, my uncles are saying that the will has no VALUE as the time to probate the WILL has passed (that is 3 years) and my younger uncle is claiming a share in that plot. My elder uncle has agreed to give 1000 sq. ft. to my younger uncle and forcing me as well to give 1000 s. ft to my younger uncle. Now, It raises a suspicion on the time it took for my elder uncle to reveal that there is a REGISTERED WILL in my name. I also tried to search the registration paper of the same plot in the registry office of my hometown, but because of the unorganized system and venality in Bihar, I could not find the record of the registration, however, I will try my best to search it again as I am presently living in Delhi. I BELIEVE, that my elder uncle may have got the records of my registration manipulated and has got a WILL made in his 2 son's names, reducing my share from 4000 sq. ft to 3000sq.ft. Now my uncles are selling that plot (their share as per the will). Can I get an undertaking (EKRARNAMA) signed from my elder uncle saying that if I am successful in finding my registration paper, he will have to compensate either 1000 sq. ft of land or monetary. If he refuses, it could show that there is a registration of 4000 sq. ft in my name instead of a WILL of 3000sq.ft only. Also, am I bound to give a share to my younger uncle, if there is a REGISTERED WILL in my name?