Drain pineapple, reserving liquid in 1-qt liquid measuring cup. Remove 1 Tbsp of the crushed pineapple; set aside for garnish. Add enough cold water to reserved liquid to measure 3 cups; pour into large saucepan. Bring to boil; remove from heat. Add gelatin; stir at least 2 min. until completely dissolved. Add cranberry sauce; stir. (Gelatin mixture should be thick.) Pour into large bowl. Refrigerate 1 1/2 hours or until slightly thickened (consistency of egg whites). Stir in remaining pineapple, apples (and walnuts if desired); stir gently. Pour into medium serving bowl. Refrigerate 4 hours or until firm. Top with reserved pineapple (or some thin apple slices) just before serving. Makes 14 servings, 1/2 cup each.