(define nodes-down (lambda (n node-list) (if (= n 0) node-list (nodes-down (- n 1) (node-rest node-list)))))A: No, because nodes-down hides details of the representation of a node (it only calls itself and node-rest).
Moral of the Story:
If you hide as much implementation detail as possible when coding ADT operations, changing the ADT representation is much easier.