التوهج والإشراقة

Not really. "Glow" products (vitamin C, antioxidants) improve overall radiance and protect against future dullness. Spot-targeted brightening uses different actives — TXA, alpha arbutin, azelaic acid — aimed at fading existing marks specifically.

Yes, but not layered directly on top of each other the same night at full strength when you're starting out — alternate nights, or use the toner in the evening and vitamin C in the morning, until your skin tells you it can handle both.

Usually sun exposure without SPF degrading the vitamin C's effect, or product oxidation from air and light exposure once the bottle's been opened a while. Both are common and both are fixable.

Sunscreen and antioxidants do different things — sunscreen blocks UV before it hits skin, antioxidants neutralise the damage that still gets through. They work better together than either alone.

Usually a mix of unshed dead skin, dehydration, and lack of antioxidant protection building up over time — none of which is about melanin at all, which is why pigmentation treatments don't fix it.

Yes — over-exfoliated skin gets reactive and inflamed, which reads as dull and uneven in its own way. Two to three nights a week with a chemical exfoliant is enough for most people; daily is usually too much.