DDNS with Caddy as a reverse proxy server

[Swindiff]

I am trying to make my server as secure as possible, so another option is limiting access to user accounts to specific devices. I created a test account and unchecked all devices, but I can still access it on my phone. Is that because I have used my phone to access my own account previously? Also if no devices are checked for a new user, is there any sort of notification and approval process for having access on a new device?

Many thanks