In a large mixing bowl, combine graham cracker crumbs, sugar, and cinnamon. Melt the unsalted butter and stir it in until the mixture resembles wet sand. Line a muffin pan with paper liners and press the crust mixture firmly into the bottom of each liner. Refrigerate for at least 15 minutes.

In a separate bowl, mix together all-purpose flour, quick-cooking oats, brown sugar, and cinnamon. Drizzle in melted butter, stirring until the mixture becomes crumbly. Set aside.

Peel, core, and dice apples into small cubes. In a medium bowl, combine apples with lemon juice, brown sugar, and cinnamon, tossing until well-coated.

In a mixing bowl, beat softened cream cheese until smooth. Gradually add brown sugar, flour, and vanilla extract while mixing at medium speed. Incorporate the egg, mixing just until smooth.

Preheat your oven to 325°F (160°C). Spoon cheesecake filling over prepared crusts, filling about two-thirds full. Evenly distribute apple mixture over filling, then sprinkle streusel topping generously over each cheesecake.

Bake for 28-30 minutes until edges are set but center slightly jiggles. Cool in pan for 10 minutes before transferring to a wire rack.

Once cooled to room temperature, refrigerate for at least 2 hours. Drizzle with caramel sauce and top with whipped cream if desired before serving.