I have stuff on the 7th screen and I've expected to be able to reach it on left swipe from homescreen, but it is not so. How can I configure it ? Does it require some non-default launcher?
If you're using the original Samsung supplied OS with Samsung's Touchwiz interface, then it doesn't wrap around, to get to the 7th screen you have to scroll seven screens to the right.
Alternatively you can "pinch" zoom out on any of the home screens to zoom out and see an overview of all of your screens, and tap any of them to move straight to them. You can also add and remove screens (up to 7) from here, by dragging unwanted screens to the trash bin at the bottom of the screen, or clicking the plus sign to add another (up to 7).