If you are doing the proper configuration this should not be a problem. However, from the error in your first post I can see that the runtime version in production is not 4.0, at least according to the error message.
So, can check and make sure that the:
1) Application pool under which the application is running is 4.0
2) The runtime of the hosted website is set to 4.0. (Right click on the project, website properties)
3) You use Telerik.Web.UI for .NET 4.0
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