Please, review the following article for a variety of ways to specify the skin of the controls - http://www.telerik.com/help/aspnet-ajax/introduction-skin-registration.html
. In your case the best option is to use the web.config AppSettings key approach:
As far as your second question is concerned, I will need a sample runnable application that reproduces the issue so that I can check it on my end. For that I suggest you open a support ticket and attach the project in there.
Hope this helps.
the Telerik team
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