Authentication for External Customer and allow internal Users

I am trying to create a self service portal for our customers (external users) and the same portal should be accessible by internal users within the organization using AD login so that they don't have to create separate logins.

Also, the portal should also allow login using social media integration and personal email like outlook.com, live.com, Gmail etc.

Technology: Self service portal will be deployed to Angular UI and Database is SQL Server.

Question 1: Is it possible to do that? If yes, how? and is there a architecture diagram to understand?

Question 2: How do we maintain permissions in that case? For each customer and for internal users?