Drain pineapple and keep juice. Cut apricots into small pieces. Dissolve Jello in boiling water. Add 1 c reserved juice. Let set until slightly thickened, then stir in fruit. Pour into pan and cool completely. Cook and stir remaining juice, sugar, flour, egg, and butter on low heat to make topping. Let topping cool. Mix into whipped Dream Whip. Spread over set Jello and top with grated American cheese.