Mobile feature

Hello, i wanted to buy Download Manager Pro, but first I need some clarification.

1) App Mobile (Android & IOS) can be used only by the administrator, or even other users can download and use an app to manage your account propi Download Manager?

2) If the answer to the first question is yes, the user how to synchronize the app with API key?

3) You can generere multiple API Key for each user or is not necessary?

4) Can I constrain users only view your files even via mobile?