All project should be upgraded to use the same Telerik Reporting version. Major releases can co-exist on the machine, but cannot be used and work together in the same application. Also Visual Studio will load only the items for the latest installed version and if the opened project is upgraded to it.
For more details, please refer to the following articles:
New HTML5/JS REPORT VIEWER with MOBILE AND TOUCH SUPPORT available in Telerik Reporting Q3 2013! Get the new Reporting version from your account or download a trial.