How can we register property after 11 years

Respected Sir, My in laws are staying in Andheri their building was redeveloped and they had received possession 11 years ago.During that time they received a copy of development agreement and possession letter and agreement which is not registered(we came to know now.).while they where given possession committee said all papers are clear and no formality is pending .every member have received same papers. my Inlaws have approached bank for loan .due to which they came to know property is to be registered .then only they will be able to give loan against it .bank want property to be refelected in esearch . we have had word with various lawyers but no one was able to help us out ..currently one lawyer have made and agreement in which all details are mentioned that this property was handed over to us 11 years ago and all details and we are registaring now he said if builder agree we can get it registered .When i approached builder first he said it is not possible to register now and was saying we need to aproach building committie during that time i said you have redeveloped building you have given flat so for registration we will need you or your authorises person he said share agreement his advocate will read if ok then he will think .he said he will not sign on any thing showing current date.He is ok showing then and know (this where terms used by him) .Kindly guide me best solution where I wont need to pay 10 times penalty and also get my property registered. Thank you in advance for all your valueable time and knowledge . Regards, Sonu Vyas.