Login Page in Xamarin Forms

Hi guys,

I am really new to Xamarin so help is much appreciated

Here are my questions:

1. I am wondering since i read the other thread about creating a login module which it says "push the login page modal on the navigation stack and pop it when you logged in" ? Is that how we create login in Xamarin?

2. So what's the difference between Question 1 Vs Creating a new login activity in the PCL and make that activity first to run on App.Xaml.cs , and after the login is successfull, we direct them to our Main Page (In my case i use MasterDetailPage Forms for the main page) ?

3. How to store login state, so when users did login once, they do not need to enter login credentials everytime they open the app until they clear the cache in options?

Kind Regards,
Kevin