Boil salted water in a large pot. Add pasta and cook 10 minutes or until al dente and then drain.
In a medium saucepan, combine reserved juice, sugar, eggs, salt, and flour. Cook until thick, stirring constantly. Remove from heat and add the lemon juice and cooked pasta. Refrigerate for 2-3 hours or overnight.
Beat heavy whipping cream and powdered sugar together with an electric mixer until stiff peaks.
When pasta is cooled, stir in the pineapple, oranges (reserve a few if serving in individual cups), coconut (optional), 3 cups of the whipped topping, and marshmallows. Mix together and refrigerate until ready to serve.
If serving in individual cups, top with the leftover whipped cream and extra mandarin oranges.