How is registration/authorization through SOC. network using oAuth2 if one of the social.networking does not give email/phone?

Website do on Laravel to authenticate via oAuth2 using the package Socialite with the right providers.
Gave rise to the following questions:
1) How to register/authenticate the user on the website, such as through the social. Facebook, if his account is only the phone (without email), and faysbuk, the phone user does not return?
2) for example, on the site Classmates through Facebook to come possible. But then the user turns out no phone no email and no Facebook login to Classmates will not be able (if there do not specify a username and password)!?
3) did I understand Correctly that most websites (Facebook, VK, Google,...) do not return the user's phone?