Don't condition for usergroup. Just select the usergroup you want the action to apply to for Access. There's not really a way to test that they're not in a specific usergroup though as there's no real event for that or condition for that.
There is no list of conditions as they're raw HTML, text, or substitutions. You can find substitution usage information below though.
www.joomlapolis.com/support/tutorials/107-use-cases/18353-using-substitutions-throughout-cb
If you really need to test for a usergroup in a condition you can try using the below type usages.
Left: [cb:if gids includes "2"]1[/cb:if]
Operator: Equal To
Right: 1
The above has a substitution IF statement that checks if the user is a Registered user. If they are it'll return a 1 and cause the condition to match.