I am uploading my iOS app to appstore connect, I have a doubt
should I upload version 1.0? Can App Version be less than 1.0 like 0.9.0 or 0.9.1
If I use any of the above mentioned version, will apple reject my app.
Please help.
It doesn't matter. Version number visible in Appstore is the one you will set up when submitting. The first time you upload your build you can set any version number 1.0 or 0.9.0, then you should increment your version number and/or build number, otherwise itunesconnect will reject your binary.
P.S. you can find it useful: https://developer.apple.com/library/archive/technotes/tn2420/_index.html