Can Azure-AD B2C use a mobile telephone number as a username?

Question

We have a mobile app and website. We would like to use Azure AD-B2C for authentication. We are not going to allow any third party authentication, but instead just use Azure

Answer 1

I could use a mobile telephone number to sign up as the username for the local in the built-in sign-in or sign-up policy. The process like the following:

And the result is:

Or you could also use the custom policy to make this just like Chris Padgett said.