Prepare the Pudding Layer:

1. Mix the Pudding:
   In a large mixing bowl, whisk together the vanilla instant pudding mix, milk, and vanilla extract. Whisk until the pudding thickens, about 2-3 minutes.

2. Whip the Cream:
   In a separate bowl, beat the heavy cream until stiff peaks form. You can use a hand mixer or stand mixer for this step.

3. Combine the Pudding and Whipped Cream:
   Gently fold the whipped cream into the pudding mixture until well combined. This will create a creamy filling for the cake.

Assemble the Cake:

1. Layer the Graham Crackers:
   In a 9×13-inch baking dish, layer the bottom with a layer of graham crackers, slightly breaking them to fit the pan if needed.

2. Add the Cream Layer:
   Spread half of the pudding mixture over the graham cracker layer, smoothing it into an even layer.

3. Add the Apple Layer:
   Sprinkle half of the diced apples over the pudding mixture. Drizzle with ¼ cup of caramel sauce for added sweetness.

4. Repeat the Layers:
   Add another layer of graham crackers, followed by the remaining pudding mixture, then the remaining apples. Drizzle with the remaining ¼ cup of caramel sauce.

Chill and Serve:

1. Chill the Cake:
   Cover the dish with plastic wrap or aluminum foil and refrigerate the cake for at least 4 hours, or overnight if possible. This helps the flavors meld and the graham crackers soften.

2. Garnish and Serve:
   Before serving, drizzle with additional caramel sauce and sprinkle with chopped pecans or walnuts, if desired.