Hello Nitin Vikraman,
The only way to get the Trial popup is to use the Trial assemblies instead of the Dev ones. Please double-check whether you work with a Dev version. It will be best if you uninstall all RadControls versions, clear your GAC from Telerik assemblies and reinstall the latest Dev version. In addition, please note that the assemblies stored in GAC have higher priority than the assemblies in the bin folder so if your clients have the Trial assemblies installed in their GAC, they will get the Trial popup.
All the best,
the Telerik team
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