I have answered your support ticket with the same question and I am pasting the information in case someone else is having similar questions. Let's continue the discussion in the ticket until we reach a resolution so we can post it here after that for the community.
It seems that some automation did not go through, probably because of some specific permissions on the concrete machine. I suggest you perform a manual upgrade which takes only a few minutes and ensures the correct assembly references in the upgraded project: Manual Upgrade Process.
The fact that window.$telerik is undefined means that the core Telerik UI for ASP.NET AJAX scripts are not loaded (yet) on this page. This can be due to many reasons like broken network requests, or by our jQuery being registered on a page without our core scripts. For the former see here, for the latter, see here, or modify the script to have the necessary checks, or make sure to use our jQuery only with our controls.
On the screenshots - we add the .noConflict(true) call to move the jQuery object that we carried to the $telerik.$ reference so we don't pollute or overwrite a jQuery instance in the global scope. You can read more about it in the following article from jQuery: https://api.jquery.com/jquery.noconflict/. The last line is a fix for an issue they silently removed, you can read more about it here: https://www.telerik.com/forums/known-issues-and-important-changes#Xrl0FgPrQkent9x6ZSCLHA.
If the information above and in the linked articles does not help you resolve the issue, can you send me a small runnable version of the project (delete unecessary files, just leave the csproj file, the web.config, a simple form that showcases the problem, and the Telerik.Web.UI.dll assembly in the ~/bin). Once I can reproduce the problem I will be able to offer a more concrete answer.
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