Yes, custom domains with /admin work.

Add /admin after the store URL.

Yes, both methods are supported.

Using the “Forgot password?” option on the login page.

The current device also gets logged out.

Yes, users can log out individual or all devices.

In the Security section of account settings.

Yes, device and login activity can be reviewed.

Backup login codes used if authentication methods are unavailable.

Yes, users can configure primary and backup methods.