Patta vs relinquishment deed

Background: 1) My father bought the current house (1974) we are staying and am planning to secure home loan to expand it. 2) My father is no more (passed away in 2004) and my mother and self (only son) are the legal heirs, we have the legal heir certificate and death certificate 3) The Sale Deed that we have is of my father's and we do not have Patta, while property tax is on my fathers name 4) We are not planning to sell our house but we want to ensure that we get planning approvals and loan eligible (from title standpoint), we were told Patta update is mandatory (for plan approvals, loan processing) 4) In this context, I believe executing a relinquishment deed may not be needed. 6) Till date, we have been paying our property tax in my father's name and paid up to date. Questions: 1) Is point #5 correct and the only thing we need to do is to get Patta updated ? 2) What is the procedure to have Patta transferred/updated? 3) Now that my father had passed away in 2004, will this delay be an issue ? Thanks in advance and looking forward to guidance. Please let me know should further information be needed.