Blepharoplasty. age is not the defining factor in choosing blepharoplasty. Have your eyes evaluated by a board certified surgeon with expertise in eyelid surgery.
Yes. For a persistent deformity.
Not usually. It is usually recommended when there is excess skin in the upper eyelids or bags under the eyes.
Yes. Blepharoplasty at a young age (even 19) is common amongst some asians seeking to create a "double eyelid" fold. Otherwise, and in my experience it is a procedure only rarely performed (and on the lower eyelids only) on young people who have inherited bags beneath their eyes (very often in girls from their father). If prominent, these bags never disappear and only worsen with age.