Place Granny Smith apples in a saucepan over medium-high heat; stir in brown sugar. Cook, stirring occasionally, until brown sugar thickens, 5 to 10 minutes. Stir 1 pinch cinnamon into apple mixture; pour into graham cracker crust.
Combine gelatin, 1 tablespoon cinnamon, and salt together in a saucepan; stir in sweetened condensed milk and eggs. Let gelatin mixture stand until dissolved, about 1 minute. Place saucepan over medium-low heat; cook and stir until mixture thickens, 7 to 10 minutes. Remove saucepan from heat and stir in applesauce until thoroughly mixed; pour over apple layer. Chill until set, 2 1/2 to 3 hours.