Keyboard Shortcut for Preferences is [Ctrl+, ] (English keyboard)
Screen-clip is for Windows:
"Versions" are the old Processing 'engine' from previous versions of Lightroom.
Changing Versions will limit the editing Tools available and set the interface to look like an earlier version of Lightroom. Keep on Version 5.
The Correct Answer is still applicable to you.
Try disabling GPU acceleration in Lr Preference performance panel. And go to your video card manufacturer's website and make sure your video driver is up to date. If there is a newer driver available, you can try turning the GPU back on after you install it.