Do we need to register landlord tenant agreement under pagdi system

Do we need to register the agreement with government, done between landlord and us ( new tenant ) when purchasing flat under Pagdi system ? Do we need to prepare and register the agreement with current tenant aswell who is selling the flat to us ( new tenant ) ? Can we do sub-leasing or create sub-tenancy, should this be included in the agreement with landlord ? Can we include clause in the agreement with Landlord, stating that tenancy would be transferred within direct blood relation without any further transfer charges e.g. from father/mother to son/daughter etc. Thanks in advance.