This app doesn't work? http://www.tp-link.com/en/download/NC200_V1.html#Apps

1. Not the same. You should pair them to make them talk to each other. 2. If you want to usre the same SSID and security settings as the main router, you can clone Wi-Fi by the button. Also you can...

If none of them are checked, nobody can see the router from outside. No worries.

There is no TP-LINK driver for T4U to run on Windows 10. It is plug and play on Windows 10 as the system itself has the built-in driver.

That the top signal light is solid green indicates the good location of WA860RE. Try cable connection to range extender. It should be better than wrieless connection to WA860RE.

Plusnet provides ADSL or VDSL for you? How about status of ADSL light when you plug the telephone line to D2? What configuration parameters did you get from plusnet? VPI/VCI, connection type,...