I currently have Lightroom as a stand alone version on my PC. What happens to my stand alone version when I upgrade to the creative cloud and if I want to discontinue the creative cloud, will my stand alone version still work?
A little more information is needed. What are you currently running?
Assuming you are running Lightroom 6, then when you upgrade to Lightroom Classic, your catalogue is converted to a new format. This breaks any returning to Lr6 unless to choose to restore a backup from before you upgraded.
There's no going back, but why would you want to? Previous versions of LR are now "frozen" and no longer supported by Adobe, which means new cameras are not supported, and any OS compatibility issues that will inevitably arise as Microsoft and Apple continue releasing new operating systems will eventually leave you stuck without a solution. And, of course, you don't get any new features. Adobe invests in rolling out new and useful features frequently to ensure that we feel we're getting our money's worth.