Your "ScoreHard" is a local variable to the group "Hard".
It means that because of the scope ("range") of local variable it can only be accessed from and only from within this group (to be displayed/modified).
This code should work.
I haven't tested it, your coding is far too much spread imo, you're using too much useless groups and too many event sheets (C2 isn't C++, try to keep your code organized in another way).
Consult this manual entry
as well as this
thread (listed in the How do I FAQ