In addition to my first reply.
You can try setting the IsDirectionReversed property of the RadSlider to True. You can take a look at the Direction
help article in our documentation where this property is described. This way you can reverse the top tick placement values from 10 to 0 and use IValueConverter to set the bottom tick placement values from 0 to 10. For your convenience, I have modified the project from my last reply to demonstrate this approach give it a try and let me know if it works for you.
As for your second question.
You can try creating a reverse collection of the slider double collection. Then you can subscribe to the ValueChanged event of the RadSlider. In the event handler, you can get the index of the selected value in the slider collection and use the same index to get the value of the second collection which represent the bottom values. The attached project demonstrates this approach.
Telerik by Progress
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