Thanks for writing and for your questions.
1. Everlive is Telerik's new mobile-app Backend Service. It allows you to create projects - representing your application, and content types - representing the different types you are working with within your application. Everlive has an out-of-the-box infrastructure for social login and user management. Additionally, you can specifiy roles and granular permissions. The Telerik Cloud Controls for Windows Phone suite is fully integrated with Everlive with plans to extend it with support for other popuplar Backend services as Azure which is already partly supported.
2. Since our CloudLogin control uses the Social Login feature of Everlive, it basically takes the user's Facebook authentication token and registers a user with that token within your Everlive's project users' base. That means if you simply replace the login functionality with CloudLogin control, you will have to make your users login again with their Facebook credentials which will create a new account within Everlive automatically.
Since it might be so that I do not understand your scenario fully, please feel free to provide us with further details about your users management story.
3. Yes, our Everlive SDK allows you to link different Social Network accounts to a single Everlive account and let the users login with different social login providers.
Do not hesitate to get back to us in case you have further questions or need assistance.
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