Is vitamin c serum for skin whitening a permanent solution? If I stop using this, will my skin become dark?

Hi, Vitamin C serum does not deliver a permanent skin whitening effect and no other treatment will do the same.  Basically vitamin C is an antioxidant which repairs your skin and makes it look more rejuvenated. Discontinuing vitamin C might not darken or harm your skin , but the rejuvenation will fade might as well the damage from the sun on your skin will not get repaired. Try chemical peels and safe skin lightening agents which can give you a satisfied result. Meet a board certified doctor to guide you properly. Good luck.