Now i'm solved on build issue by build project "Telerik.Windows.Themes.Vista" then back to open project "Vista".
I assume "Telerik.Windows.Themes.Vista" has responsibility on merge "*_x.xaml" and create *.xaml".
I want to modify your buil-in theme follow below controls.
How i know the difference between Q2 & Q3. I saw xaml file structure and template structure are some changed.