• Gift Deed made by Donner without ownership and illegal occupied

Year 1972 we started living in joint family on rented house Room no 1 &8  in Mumbai on Paghadi System. Rent receipt used to come on my Uncle name from 1978, My father got married and started living separately in Room No 8 after 28 years stayed in same room no 8 and my uncle in Room no 1.

Year 2000 my building Landlord and Builder came in agreement of constructing new building by demolishing old structure and Builder will provide old tenet flat in same building with extra area on the basis of Ownership to the old tenant. Since my father was tenant by rent receipt but by physical occupation of premises builder had agreed to give 2 separate flat against room no 1 and 8. Agreement signed between my Uncle and Builder.

Year 2002 Building got ready for occupy we got the possession of the flat , but builder did not provided spate Sale deed for 2 flats. Only we had one agreement copy alternate accommodation long followup of 3 years with builder did not turn up, my uncle registered the agreement at registrar office by declaring 403 Flat Belongs to My father and 303 Flat belongs to my uncle on ownership basis, stamp duty got paid along with attaching year 2000 alternate agreement in the same agreement also written 1 flat will be given to my father on ownership basis and one flat to my uncle on ownership basis.

My father and we stayed in same flat Mumbai from 2002 to 2008 and then my father due to agriculture activity in our villige decided to move Gujarat and I moved to different city for job. We had give flat on rent from year 2008 to 2016 all rent agreement got registered at registrar office till June 2016 tenant was staying in the Flat no 403. 
Last month Tenant vacated the flat and My Uncle and his Son illigaly bricking lock of the flat started living in the flat we came to know we visited the flat they threatened us do not even dare to come in the premises now onwards, they are calming they are the owner of the flat.

After long research we came to know my prepared the Gift Deed he had given to his son and they did registration at registrar office in year May-2015 as witness my Aunty and uncle daughter had singed in gift deed.

Since agreement was one between two flats and my uncle name it was registered my uncle took the advantage of signature authority and gifted my father flat 403 to his son. Whereas agreement clearly written 403 Flat belongs to my Father only.

Now my Father had compliant police station no action from department yet, my father Age is 70 and my uncle age 78.  

IF we file case in high court and my uncle who did fraud die then case will continue or not? How many year it will take for Sr. citizen case to be resolved in high court is there any way to speedy process.

Since builder not provided Separate Sale deed all these issue occurred, can we file case against builder as well? 
In above case which are the section of law will be applicable? Please advice. We have all the documents backing up related to property and society registration details as well.