E Stamp for flat in Greater Noida U.P

Hi, Need clarification on following points. 1. What is E stamp validity in Noida extension U.P. Is there any new rule for validity of e stamp in U.P. 2. What should be the consideration of property amount in E stamp. Circle rate Value on which e stamp calculated Or Actual BSP price+parking which is less than circle rate. Or we can keep it blank thinking that additional e stamp may required, since builder not doing the registry immediately but asking copy of e stamp for giving possession. 3. If validity of e stamps rule comes, will applicable to E stamp issued earlier. 4. Additional amount of e stamp can be purchased for same flat if it's required later on and it's ok for doing registry.