Is the treatment for teen and youth acne different from the treatment for adult acne?

No. Adults with true acne use the same treatments as teens use. (rosacea in adults can be confused with acne, but has different treatment). For true acne, over-the-counter benzoyl peroxide gel/cream is helpful. Doctors can add antibiotic gels. If more help is needed, retinoids such as Retin-A or differin (adapalene) gel can be used instead of benzoyl peroxide. Oral contraceptives & oral antibiotics are options.
No. Acne is caused by the same three things independent of age. Increased oil production, blocked pores and bacteria.