Transfer of ownership of flat from father to son

My father died on 06/03/1994 ,he bought a mhada flat through lottery system in 1983,allotment letter and allotment order Xerox copy available with me ,after my father's death in 1994 society in which our flat was there was registered and share certificate was issued to every member except us,hence we do not have share certificate of this flat,after my fathers death my uncle sent my mother to village with my sister and kept me with my uncle at uncle's residence in worli .my uncle took possession of my father's flat at jogeshwari(Mumbai) and gave it on rent .After completing my 11th my uncle sent me to my mother but did not give possession of flat.After 12 the I am demanding uncle possession of my fathers flat but he is cheating me that he will give me flat next year and transfer ownership of my fathers flat society is demanding succession certificate and advocate is telling letter of administration is required. my father was working with Indian railways and I got job in railway on compassionate ground and also my mother is getting pension from how can I obtain my father's flat from my uncle and also transfer its ownership to my name.details. My name -Sandeep Satish Kamble, fathers name late Satish Janardan Kamble(Sr.Section Officer/Western Railway/ Church gate) Property address-room no -1053,chawl no-146,sneha bandha co op society ltd,sarvodaya nagar,mhb colony, meghwadi,jogeshwari(e)400060