I understood first para but i didnt understand 2nd para :
In the sample page you would end up having the Authenticate User server behavior 4 times on the page. Twice for form login and twice for auto-login. Just copy the two that are already there in code view and then edit them so one uses phone number and edit the redirects keeping everything else the same.
This is for logged in page?
FYI, sign in won't have auto login & remember me function.