Two (interesting?) drag and drop questions

Hello again

still experimenting before purchasing but getting very close...

(a) Is there some way to unassign a true/false variable so that it does not have a value set and therefore does not trigger anything? I know I could play with number variables but a boolean is what I really want.

(b) I would like learners to be able to change their drag and drop choices. One of the choices is to return all the drag and drop items to their original positions on the screen (i.e. not on a drop zone). I know how to do that. However, is there some way that I could also reset the variables associated with each object? At the moment, variables are set when the dragged object is dropped on a receiving object. However, they are not unset when they are returned to their original position (which is what I would like).

I hope my explanations make sense.

Thanks for any help

Andrew