Press Sauté on Instant Pot. Add star anise, cloves, cinnamon, coriander, and peppercorns and sauté until fragrant, 3 to 4 minutes. Add ginger and onion and cook, stirring occasionally, 4 minutes. Add apple, chicken, 5 cups water, and 1 tablespoon fish sauce; cover and lock lid. Cook on high pressure 22 minutes. Use natural release for 10 minutes, then release any remaining pressure.  Transfer chicken to plate. Strain broth, discarding remaining solids. Return broth to pot, add noodles, and let sit until tender, 3 to 4 minutes. Meanwhile, shred chicken, discarding bones. Return to pot and stir in remaining Tbsp fish sauce. Serve with desired toppings.