Combine first 5 ingredients in a bowl, stirring well. Dip pork cubes in batter, a few at a time, coating well. Pour vegetable oil to depth of 1 inch into a large heavy skillet. Fry pork in hot oil over medium-high heat 5 to 6 minutes. Drain on paper towels.
Drain pineapple, reserving 3 tablespoons juice. Combine cornstarch and reserved pineapple juice in a Dutch oven, stirring well. Add sugar and next 5 ingredients; stir well. Cook over medium heat, stirring constantly, until thickened. Stir in pork, pineapple, oranges, and green onions; cook just until thoroughly heated. Spoon pork mixture over rice.