There is no built-in functionality that will make the rotator "rewind" to its first item, after all items have been displayed. The only way to achieve the desired effect is by using some custom code, and setting the right scroll and frame duration. For example, if you set FrameDuration="0" and ScrollDuration="100", to the rotator in the following demo: http://demos.telerik.com/aspnet-ajax/rotator/examples/default/defaultcs.aspx, the items will be scrolled very quickly.
There is no built-in way to retrieve the number of the currently shown items in the rotator's viewport. If the items have fixed dimensions (fixed ItemWidth and ItemHeight), then it is easy to compute how many items are displayed. Otherwise, it is fairly complicated to determine the number of the items in the viewport. The same is true, for the dimensions of the items.
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