**Prepare the Crust:** Preheat the oven to 350°F (175°C). In a bowl, mix graham cracker crumbs, sugar, and melted butter until well combined. Press the mixture firmly into the bottom of the springform pan. Bake for 10 minutes and set aside to cool.

**Make the Cheesecake Layer:** In a large bowl, beat cream cheese and sugar until smooth. Add eggs one at a time, mixing after each addition. Mix in vanilla extract and sour cream until just combined. Pour the cheesecake batter over the cooled crust.

**Prepare the Apple Topping:** In a saucepan over medium heat, melt butter and stir in brown sugar, cinnamon, and nutmeg. Add diced apples and cook for 5–7 minutes, stirring occasionally, until softened. Set aside to cool slightly.

**Make the Crumble Topping:** In a bowl, mix flour, oats, brown sugar, softened butter, and cinnamon until crumbly.

**Assemble the Cheesecake:** Spoon the apple topping evenly over the cheesecake layer. Sprinkle the crumble topping over the apples.

**Bake:** Place the springform pan on a baking sheet and bake for 50–60 minutes, or until the center of the cheesecake is set but still slightly jiggly.

**Cool and Chill:** Let the cheesecake cool at room temperature for 1 hour, then refrigerate for at least 4 hours or overnight.

**Serve:** Remove from the springform pan, slice, and serve.