I saw this UI guideline http://www.developer.nokia.com/Commu...mples_provided
where it mentioned that

Back button is used to exit views and the app
Now I have a question on this back button operation.

Let me give you a scenario :

When I launch the Ovi Store application it brings me the home page with a toolbar at the bottom. There is the Cross (X) button on the left of the toolbar. But when I click on any of the application to download a new page comes up and theCross(X) button changes to a Back(<--) button. When I click on the Back button it navigates to the previous page and once I am back to the home screen again I see the Cross(X) button. And to close the app I click the Cross(X) button.

Now according to the guideline , does it mean that we should NOT use Cross(X) button at all, rather there should be only one Back button, which should perform differently in different situations. Like when I am in Page2 and click the Back button it will bring me to the home screen and on home screen when I click on the Back button again it closes the application.