1) If I have the current Beta Application on TestFlight say version 1.0.2 and 1.0.1, I want to upload 1.0.2 to App Store for reviewing. Will this affect the current testing from using the installed beta 1.0.2 version.
2) Once the 1.0.2 version on live (in appStore), will I be able to use testFlight for beta testing in later version say 1.0.3?
1) You can submit the 1.0.2 version to Apple for review and users will still be able to test it through TestFlight.
2) Once 1.0.2 goes live in the App Store, you can submit later versions, like 1.0.3, to TestFlight, but you'll need to create a new version entry for your app in iTunes Connect. The 1.0.2 record will be locked.