Apple release a new feature of the App Store. The ability for owner of iPhone with non compatible iOS version to download a previous (the last compatible version) of your Ap
I believe I have the answer, after looking in the iTunes Connect Developer guide. It says:
You can also indicate a legal issue with your app, including previous versions, from the footer of the “Rights and Pricing” page. Indicate a legal issue with your app by selecting each version of your app that has a legal issue. You cannot select a version of your app that is ready for sale. If the version of your app that is ready for sale has a legal issue, you must submit an update for the app and indicate the legal issue during submission.
Apparently, indicating a legal issue will prevent users from downloading previous versions.