Division of property and possession among brothers

Hi My father are 8 siblings in total. 6brothers and 2 sisters, all are married and have children. My grandmother passed away 3 years back. My grandfather is alive. we have around 4 acres of ancestral property and 2 acres of property is bought on my grandfathers name. also 10 acres of land was bought in all 6 brothers name. Each land is agricultural land. At 10 acres of separate land my fathers elder brother is residing from 15-17 years. At our 4 acre ancestral land and 2 acre bought land my fathers 3 younger brothers are residing. My father and one of his elder brother are living in different cities on their own properties. My father asked for division of our agricultural land but his brothers are not dividing . They are using my fathers land and he does not have possession there as he never lived there. please respond to my below queries: 1 How my father can ask for division legally 2 How to get legal possession of property 3 My uncles try to threaten when my father talks about separation. 4 Can my father sell out his share of property without division. Thanks Pradeep