In order to develop for the platform, you need to register your application[0], and your device[1]. Also you cannot even run your own application without getting google's approval[2], which costs $5..
Then, at runtime, the device will first validate that the app you are trying to run was validated, sending the `AppID` to google.
I have had issues running a wifi dongle when connecting using the tv's usb port - admittedly this is with the old version and not the new one with the updated power circuitry.
However, I have had no issues using usb power from the tv with a LAN connection - this is using Kodi which I suspect will increase the power pull. YMMV