The best way to check installed products is using the installed apps in the Windows settings. CC3+ itself isn't really aware what a product even is, because all the installers does is to add more files to the relevant folders.

To check inside CC3+, you kind of have to know what is supposed to be there. Do you have the expected templates for the product for example? Or the expected symbol catalogs. Try loading up an example file belonging to the product, is it full of red X'es?

Your DD3 installation seems to be missing a lot of stuff. Here's what that location should look like

It looks like you maybe don't actually have DD3 installed at all just some random folders that have come with various annuals.

Note that there is no reason to go around remembering the EDITSHADING command from step 3, simply using :CC2EDIT: on the shaded entity will do the same job.

I'll need to refer you to their support then though. If this software provides additional services on top of windows for handling the files in their fences, only those who know that program would know if it stores a full copy or a link of things you put there.

Given the message you got, I would assume a full copy, but that's just blind guessing.

It should be easy enough to test though. Just create your own sacrificial folder with some junk files or copies of existing files in it, then add that to your fence, and then try to delete it again and see if anything happens to the original. Since this isn't related to CC3+ in any way, the behavior seen with that folder should be the same as with the CC3+ folder you added.

You don't need to install on c:\

What happens when you install CC3+ is that a very tiny portion of the program is always installed on C no matter what you pick in the installer. The bulk of the program is installed to wherever you pick in the installer, and it is fine to put that on any drive (Should be a local drive though, not external drive or network drive)

If you have parts that seems to be installed outside the data directory, it might be that you have performed an artwork-only install on those components. This type of install is intended for people not using CC3+, but just want the artwork for use in other software. The files in these directories are NOT the complete set of files CC3+ needs, so they should not be manually copied into your CC3+ data directory. I think just re-running the installer for those "missing" products should help. The separate art file directories are just a bunch of image files, and can be safely deleted manually.