STIR boiling water into jelly powder in medium bowl at least 2 minutes until completely dissolved. Stir in cold water.
POUR into 9-inch square pan. Refrigerate 4 hours or until firm.
CUT jelly into 1/2-inch cubes. Spoon into 4 dessert glasses alternately with 1/2 cup of the whipped topping. Top with dollops of the remaining 1/2 cup whipped topping.