Thank you - now I understand why I could not find any places with Telerik traces using file contents search in Total Commander and full registry search. I thought that it could be a cache or another bin registration info that only VS can decipher.
I was going to use your advice today but suddenly discovered that my instance of VS no longer tries to load any Telerik assembly at startup. I think it happened after upgrading to the latest version 15.5.7, which was done with the administrator privileges. I already tried to launch VS with admin rights, and as I saw, some problem Telerik entries were cleared by VS itself in this mode. It seems, VS can heal itself in the admin mode :)
Thank you again for your last answer. In the future, I will know what to do to fix similar issues.