"you require permission from TrustedInstaller to make changes to this file".

Like Maria said, if you're attempting to remove the ActiveX Flash Player on Windows 8 and higher, that version is distributed directly by Microsoft.  We don't have the ability to modify those locations, which is why we don't produce installers or uninstallers for those locations.

I'm surprised that you were able to rename the folder.  You should have been limited by the same permission restrictions that you're encountering when you attempt to delete it.  If you set a system restore point before you started modifying system files, you could revert to that point.  That's probably the easiest path, but since it's typically disabled by default, unless you went through the work of doing this in advance, it's not going to help (but worth knowing about for future reference). 

https://www.windowscentral.com/how-use-system-restore-windows-10

Regardless, if we're understanding correctly and that's what happened, you're basically stuck trying to coax Windows into restoring those folders back to an expected state so that you can remove them with the appropriate patch.  I *am* a little concerned that we're not communicating clearly, and this would be a great place to include some screenshots and/or more specifics on the files and folders we're talking about.

You can try running the Windows System File Checker from an elevated command prompt:

https://www.lifewire.com/how-to-open-an-elevated-command-prompt-2618088

 https://support.microsoft.com/en-us/topic/use-the-system-file-checker-tool-to-repair-missing-or-corrupted-system-files-79aa86cb-ca52-166a-92a3-966e85d4094e

If you're lucky, it will fix it.

If not, what I've found is that removing the last Flash Player update applied by Windows Update, rebooting, and then reinstalling the update via Windows Update (since you're not trying to get back to a working Flash Player, you might be able to skip that step -- you should just be reverted to an older Flash Player at this point) might get you to a place where you can apply the Flash Player Removal patch from Microsoft successfully. 

https://www.bleepingcomputer.com/news/microsoft/how-to-uninstall-windows-10-updates-manually/

There is a theoretically non-destructive "refresh the operating system" option, but you'd be wise to make sure you had appropriate, working backups first.

https://support.microsoft.com/en-us/windows/how-to-refresh-reset-or-restore-your-pc-51391d9a-eb0a-84a7-69e4-c2c1fbceb8dd

If that doesn't help, you're probably going to have to open a support case with Microsoft.  They distribute the ActiveX Flash Player that's built into Windows 10, and are the only ones with control over the relevant installation directories.