As to your questions.
1. Yes, the backend logic will send a separate notification for each device that falls in the notification filter, independent of the fact that they have the same push token.
Usually, you may receive the same notification on the device the same number of times as there are registrations with this token in the backend. However, some times the Apple Push Notification services sends only the last one if the same device is targeted with multiple notifications for a very short interval of time.
In production setting you are rarely expected to stumble upon such case because the user is unlikely to install and reinstall the app a few times within a short time span. If the app has been uninstalled the device will be likely marked as inactive in the backend and no notifications will be sent to it.
On a side note, I believe that you are aware how you can extend the client code (as explained in this forum thread
) to persist the Id between installations, if needed at all.
2. At the time of testing you may remove them manually from the portal or from the REST API. In production environment perhaps this will occur rarely if at all.
Let me know if you have questions.