Share/ Entitlement in joint property

My late father had two marriages. From the first marriage I am the only son. My mother expired more than 60 years back when I was only 3 years old. After this, my father married again. From the second wife he has 4 sons and two daughters, all of whom are married and well settled. With his own earnings, my father purchased some agricultural land at our native place in Bihar which were registered either in my late mother's name or my name or my step mother's name. He also purchased a building in Kolkata in his own name. He did not leave any will. My querries are: 1. What is my share of property? Am I entitled to get half of the property? Do I inherit all the land registered in my and my mother's names? 2. The building has 12 flats and 5 shops, all of unequal sizes. What is my share? 3. Are the step sisters entitled to get a share? If yes, then how much? 4. Does the step mother have right to get equal share? What happens to her share after her death? Can she sell out all her share , or transfer to any one or all of her siblings except me?