So, anywhere I have a saved Photoshop File, it used to have the original icon -- the blue box with the logo in the middle.
Now, the icons has changed. Sometimes it would be the icon inside a blank page, most of the time it looks like this:
The Type is not a normal PSD. (Adobe Photoshop Document) file anymore but a Adobe Photoshop Image 13 file.
I can't open the file by clicking on it, but I have to enter Photoshop. Now, if I start creating/saving new files, it is Image 13 format.
How do I fix this?
Uninstall CC2018 and reinstall again. That should return things to normal.
Did you have any previous version installed, specifically CS6 (Photoshop 13)? At default settings, the update installer also removes any old version already installed. Unfortunately, this uninstall happens after the new version is installed, and that can sometimes cause a lot of strange problems. Some registry settings that should point to the new version, get changed in that uninstall and are left orphaned.
Rather inconspicuously, there is an "advanced options" rolldown in the installer, and here you can uncheck "remove old versions". But few people notice that. If you do wish to remove the old versions, do that before running the installer.
It was always CS6. No changes that I would recognise to have been made. I don't have CC, or any form of it.
I'll try uninstall and reinstall with the advance options advice you have provided, if it is present when doing so.