I’m really new in mobile app development, but I can make apps for android and ios. So my question is, Can I publish a free app that every one can download from the stores, but it can usable after a registration? So the initial state is a login/reg form. Every one can download, but just the approved users can use it. Can I publish this kind of app without any apple/android enterprise account? With the normal development account? Thanks.
With the normal developer account you should be able to publish this on Android.
For iOS, you'll have to provide a username and password, so that the app store review team can check it.
This can be found by clicking your app build in the iOS App subsection on the left hand side panel on iTunes Connect