How do I get rid of long standing hyperpigmentation (i.e. "permatan") on face, lower legs, and forearms?

My natural skin tone is light olive (Type III I'd say) however my face, forearms, and calves are dark brown. At 25 of the time of this post, I've been this color since 2003 I'd say. For the past two weeks, I've been using various products including niacinamide, arbutin, and azelaic acid every night. I have yet to see any result in returning to my normal skin tone. I'd like to know if my skin has been permanently turned to black or if I can opt to use aggressive "bleaching" measures?

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