Tips: Do not substitute sugar-free gelatin for regular gelatin. Make the salad and the cream cheese mixture a day ahead; chill.
Combine gelatin and boiling water in a bowl; stir until gelatin dissolves. Stir in cold water. Cover and chill 1 1/2 hours or until the consistency of unbeaten egg white. Fold in apples, grapes, and pecans.
Spoon into a 5-cup gelatin mold coated with cooking spray. Chill until firm.
Beat cream cheese at medium speed of a mixer until smooth. Add sour cream, sugar, and vanilla; beat well. Invert mold onto a serving plate; cut into 8 pieces. Serve on lettuce-lined plates; top with 2 tablespoons cream cheese mixture. Garnish with apple slices and chopped pecans, if desired.