How are active devices uniquely identified in the Mobile Services Free tier?
Active devices for a given mobile service are uniquely identified by their installation ID. For a physical device, the installation ID is typically persistent unless the app is uninstalled by the user. For device emulators, the emulator implementation controls whether the same or a new installation ID is reported each time the application is launched.
Related questions and answers
You can choose to upgrade at any time via the Microsoft Azure classic portal. Upgrade takes effect immediately.
For Basic and Standard, you can increase the number of units dedicated to a given service via the Scale tab in the Microsoft Azure classic portal. Alternatively, upgrading to a higher tier will also add capacity.