Is DX pro a separate purchase ?
Yes, it is. Due to a glitch in Impulse it shows up anyway, even if you don't actually have it installed. Ignore it and just verify DesktopX.
I suggest you uncheck pre-release versions in Preferences. That will give you version 3.5 instead of the beta for 4.0 which still needs work. Btw, which version do you have installed now?