Bring 3 cups water and rice to a boil in a saucepan. Reduce heat to medium-low, cover, and simmer until rice is tender and water has been absorbed, 20 to 25 minutes. Set aside and let cool.

Heat 2 tablespoons vegetable oil in a large, deep skillet over medium-high heat. Add onion and cook until soft and translucent, about 5 minutes. Stir in garlic and cook until fragrant, about 1 minute. Mix in cooked jasmine rice and frozen peas and carrots; fry until rice begins to brown, about 5 minutes. Add 2 tablespoons butter and stir to combine. Pour in eggs and cook until firm. Add oyster sauce, soy sauce, and 1/2 lemon juice; stir to combine. Season with salt and pepper.

Heat remaining 1 tablespoon vegetable oil in a separate pan over medium-high heat. Add shrimp and fry until they are bright pink on the outside and the meat is opaque, 2 to 3 minutes. Mix in remaining 2 tablespoons butter and lemon juice. Combine with fried rice mixture.