Re: How to log in as Administrator on a Lumia 640 LTE
Not really possible. Windows phone is designed as a single user OS because phones are assumed to be personal devices. Therefore, there is only one account and it is an admin account. You don't have to do anything special.
Windows Phone does not use "masking" to hide the WiFi tether. Your carrier will see when you tether. They may simply not allow the Internet Sharing switch to remain "On" or they may take action against you up to and including terminating your service without warning for violating their Terms of Service.