Do a derma know how to lighten dark pigment on smile/laugh line without using hydroquinone? can they only focus on problem areas & not whole face?

I think so: While hydroquinone is one of the more common and effective treatments for hyperpigmentation, there are other alternatives: tretinoin (Retin-A) creams, corticosteroid, azelaic or glycolic acid. They certainly can be applied only in selected areas. You are correct: your best approach is to work with a good dermatologist. Good wishes:)