In a 2-quart saucepan combine diced apples with water, sugar, and salt at medium temperature until the apples are done but not mushy, about 10 minutes. While apples are cooking mix cornstarch with 1/4 cup water and dissolve cornstarch.
When apples are done add lemon juice and berry juice. Cook and stir until blended. While stirring on medium heat, add dissolved cornstarch slowly and stir constantly until thickened. Add berries and cinnamon mix through. Remove from heat and cool before placing it into cooled prepared pie shell. Refrigerate until thoroughly chilled.
Sour Cream Topping
Dissolve gelatin in 2 tablespoon water and set aside. Mix the sour cream, sugar, cream cheese, dash of salt in a pan warm on low heat until sugar is dissolved and everything is mixed thoroughly, stir and watch that mixture does not burn or dry out. When all is smooth and blended add vanilla and stir.
Then gradually add gelatin until mixture has a firm consistency of soft pudding, remove from heat. Sour Cream topping may be smoothed over Blueberries while lukewarm and chill. Pie may be garnished with whipped cream.
If you are on a tight schedule you may use blueberry pie filling but the pie will taste much sweeter.