Beat 2 cups cream with 6 tablespoons sugar in a bowl with an electric mixer at medium speed until it just holds soft peaks. Reduce speed to low, then add cream cheese and mix until combined.
Spread 1 1/4 cups cream cheese mixture evenly in bottom of springform pan and cover with graham crackers. Spread with another 1 1/4 cups cream cheese mixture, followed by graham crackers in the same manner. Spread remaining cream cheese mixture on top. Smooth top, then cover pan with foil and freeze until firm, about 1 hour. Transfer from freezer to refrigerator and chill, covered, until a sharp knife inserted into center cuts through softened graham crackers easily, about 8 hours.
Pulse remaining graham crackers in a food processor until finely ground.
Beat remaining cup cream with cinnamon and remaining 3 tablespoons sugar using electric mixer at medium speed until it just holds stiff peaks, about 3 minutes.
Remove foil and side of pan and frost cake with cinnamon cream. Serve cold.