In a small saucepan, sprinkle unflavored gelatin over ½ cup cold water. Let stand for 1 minute. Stir in milk and sugar. Cook and stir over medium heat until gelatin and sugar are dissolved. Remove from the heat. Whisk in sour cream and vanilla until smooth.
Spoon 1 ½ cups creamy gelatin mixture over the first flavored layer. Chill until set. ***HINT: You do not want your extra creamy mixture to set while you’re waiting for the fruit layers to set. I leave my creamy filling on the kitchen counter and stir it before layering it on each time until it is used up.
Prepare lemon flavor gelatin as directed for lime gelatin. Alternately layer flavored gelatin with creamy gelatin layers, allowing each to set before adding the next layer. Top with cherry gelatin. Refrigerate overnight. Cut into squares. Serve with a spatula right out of the glass dish.