Create a web form that uses ViewState to store and retrieve a counter value, which increments by 2 each time a button is clicked. Extend the program to secure the ViewState using recommended techniques from the textbook. Additionally, define a Customer class and implement functionality to store three Customer objects in ViewState and retrieve them. Also, explain whether the counter value would remain the same or differ when the page is accessed from different browser windows or by multiple clients, and justify your observation.