Rinse chicken under cool water. Sprinkle 1 tbsp kosher salt on the exterior and interior of chicken. Rub to clean and exfoliate chicken. Rinse off all salt. Remove and discard any loose pieces of fat. Carefully place the chicken in a large bowl, breast side up. Sprinkle remaining 2 tbsp of kosher salt, fish sauce and sugar over chicken. (Optional: Refrigerate and allow marinate for 2 hours.)
Press saute button on the Instant pot and toast coriander seeds, cloves and cinnamon sticks for several minutes. Remove and put into spice infuser. Throw in onion and ginger and stir until aromatic. Add chicken, cilantro and apple to pot. Top with fresh water.
Press Cancel/Keep Warm button, lock the lid in place and turn valve to seal position. Set Instant Pot to Soup function, high pressure, 14 minutes. When done, turn off Instant Pot and quick release by turning valve to vent position.
Remove lid and take out cilantro, apple, spice infuser, onion and ginger. Carefully remove chicken to a large bowl. Add cold water to cover chicken to prevent it from drying and to cool.
In the meantime, skim fat from the broth. Taste and adjust the broth as needed with fish sauce or extra salt.
Cut or shred the chicken into bite sized pieces. Discard skin.
Cook noodles and drain. Place noodles in bowl. Top each bowl with chicken and ladle in soup. Place bean sprouts in and shower with herbs. Squeeze on fresh lime juice. Serve immediately.