Lmp-1st oct.1st us corresponds with lmp during 7th week, on 24th nov, i was 7.6 wks, can there be any chance that i conceived on 25th sept?need surity

Paternity test: It sounds like you need to determine who the father is...And there is no way to know the exact date of conception. It sounds unlikely that you conceived on 9/25 though, with a period after that date. But that's not 100%.

No: If your last period was oct first then you would have conceived a couple of weeks later. If you know your due date then you can look for a free online reverse due date calculator. That will show your conception date. There is a free app called due date caluclator in the apple app store too.