Hi and welcome,
Yes, all your previous Cubase projects will play in C14 (you might need to re-enable Vst2 support in the plugin manager). You might also need to update some of your plugins to their newest version.
I find it rather suspicious that you cannot even kill Cubase via the Task manager, I’ve never experienced that.
Have you tried starting Cubase in safe mode and see if that helps (Start Cubase in Safe mode / Temporarily disable preferences).
Does this happen with every project or might there be some problematic plugin involved? You could try updating your plugins to their newest version and see whether that helps.
(I think you can only attach links after a couple of posts here)