I have an app for iPhone on app store that supports all versions from iOS 4.2.
Now I’ve developed the universal app (iPhone and iPad) that supports versions from iOS 5.0
Is it possible to have this two versions published on app store on the same page as one app and that the users are able to choose which version to install on their devices?
No you can not do that. A new binary in a application replaces the old one. Creating two applications in iTunesConnect is possible, but you need to name them uniquely, so you will have two different applications in the store.