Divided them into groups

1) They divided the boys into groups for all activities.

2) They divided the boys into groups for every activity.

3) They divided the boys into groups for each activity.

In which case:

a) We have the same groups all across the board. No matter what the activity, the groups are the same.

in which case:

b) The groups aren't the same. Each activity has its own distribution of boys into groups. The groups in one activity are not the same as the groups in another activity although we have the same boys.

and which cases are ambiguous?

Gratefully,

Navi