At 19, your skin and hormone levels are still maturing. For persistent acne and dark spots, you likely need prescription-strength treatments like topical retinoids or oral medications, which a dermatologist must prescribe. Over-the-counter salicylic acid or niacinamide can help fade dark spots. Regarding beard growth, facial hair is heavily influenced by genetics and can continue to develop into your mid-20s. Do not self-medicate with beard-growth products like Minoxidil without medical advice. I highly recommend consulting a dermatologist to evaluate your skin, and an endocrinologist to check your hormone levels (like testosterone) to ensure safe, effective, and personalized treatment.