In a shallow bowl, beat eggs until blended. In another shallow bowl, mix flour and ½ cup cornstarch; season with salt and black pepper. Coat chicken in egg, then toss in flour mixture, tapping off any excess.
Into a large, deep skillet, pour oil to a depth of ¼". Heat until shimmering and a piece of chicken sizzles when added. Working in batches, fry chicken until golden brown and crispy, 4 to 5 minutes. Drain on a paper towel-lined plate.
In a medium saucepan over medium heat, heat 1 tablespoon oil. Add garlic, ginger, and red pepper and cook, stirring, until fragrant, about 2 minutes. Whisk in orange juice, hoisin sauce, soy sauce, chili sauce, vinegar, brown sugar, and lemon juice and bring to a simmer.
Meanwhile, in a small bowl, whisk remaining 1 tablespoon cornstarch with 2 tablespoons water. Slowly whisk into sauce to thicken and simmer, stirring occasionally, until sauce is syrupy, about 5 minutes.
Transfer chicken to a platter. Add sauce, toss to combine, and top with scallions. Serve over rice.
