Cookie middleware in MVC 6

I am trying to understand the cookie Middleware authentication behavior and its flow. However, I am not able to understand that. Below is my issue

1. Does cookie has to be set/get with ClaimsIdentity and not using asp.net identity ?

2. I have implemented Remember Me functionality which creates the cookie, so in this I need to use Cookie middleware OR not ?, for this I am using below code

   var result = await _signInManager.PasswordSignInAsync(model.Email, model.Password, model.RememberMe, lockoutOnFailure: true);

   So,  considering the above way how can I validate the user based on cookie ? which is the preferred way for creating cookie 1 OR 2 point ?

3. How can I validate user based on cookie using claims identity ?

Any help on this appreciated !