In medium saucepan, stir together sugar, flour and salt.
Drain pineapple, reserving juice to equal 1 cup. With whisk, gradually stir juice and egg into sugar mixture. Cook over medium heat, stirring frequently, until mixture comes to a boil. Stir in lemon juice. Cool mixture to room temperature.
Meanwhile, cook pasta according to package directions; drain. Rinse with cold water to cool quickly; drain well.
In large bowl, stir together pineapple juice mixture and pasta. Cover; refrigerate several hours or overnight.
Add crushed pineapple and chunks, oranges, 2 cups whipped topping, marshmallows and coconut; mix gently and thoroughly. Cover; refrigerate until cold.
Top with remaining whipped topping; garnish with cherries, if desired.