Mix graham cracker crumbs, melted butter, sugar, and cinnamon until the mixture resembles wet sand. Press firmly into the bottom of a 9-inch springform pan. Chill in the refrigerator while you make the filling.
Sprinkle gelatin over cold water in a small bowl. Let it sit 5 minutes until it looks spongy. Microwave 10–15 seconds until fully dissolved and clear. Set aside to cool slightly.
Beat softened cream cheese and sugar with an electric mixer until completely smooth and fluffy, about 2–3 minutes. Scrape the bowl often. Mix in vanilla. Slowly pour in the cooled gelatin while mixing on low. In a separate bowl, whip the cold heavy cream to stiff peaks. Fold the whipped cream gently into the cream cheese mixture until no white streaks remain. The filling should look light and airy.
Pour the filling over the chilled crust and smooth the top. Cover and refrigerate at least 6 hours or overnight until firm to the touch.
Melt butter in a skillet over medium heat. Add apple slices, brown sugar, cinnamon, and salt. Cook 6–8 minutes, stirring often, until apples soften and the sugar turns glossy. Pour in heavy cream and vanilla. Simmer 1–2 minutes more until the sauce thickens slightly. Remove from heat and cool completely.
Spoon the cooled caramel apples over the set cheesecake. Drizzle with extra sauce if desired. Run a knife around the edge of the pan before releasing the springform. Slice with a clean, warm knife for neat portions.