Preheat oven to 350 degrees F (175 degrees C). Place a bowl in the refrigerator to get cold.
Combine graham cracker crumbs, butter, and 1/4 cup sugar in a bowl. Press mixture firmly over the bottom and up the sides of a 9-inch pie plate.
Bake in the preheated oven until firm, about 7 minutes. Let cool completely.
Whip cream in the cold bowl with a hand mixer until stiff peaks form.
Stir sweetened condensed milk and frozen lemonade concentrate together in a separate bowl. Fold lemonade mixture gently into the whipped cream. Pour filling into the cooled crust. Freeze until set, 8 hours to overnight.
Keep pie at room temperature for 10 minutes before slicing. Toss strawberries, blackberries, and raspberries with lemon juice and 2 tablespoons sugar in a bowl. Top each slice with mixed berries.