dap77,
Let's see if I understand what you're trying to do. Your survey takers don't have to complete all groups, just the ones they want to, right?
If so, one way to do this is to present a multiple options question at the end of Group 1 asking them to select which of the three remaining groups they would like to complete. We'll call this question the branching question.
Then you can create conditions for each question in Group 2 to ask only if Group 2 was selected in the branching question.
You can create conditions for each question in Group 3 to ask only if Group 3 was selected in the branching question.
And you can create conditions for each question in Group 4 to ask only if Group 4 was selected in the branching question.
Does that help?
-Mike-