Which is now the top possible youngest age to get plastic surgery?

Depends on reason: Plastic surgery includes more than just cosmetic surgery. We routinely operate on infants for cleft lip & palate and other abnormalities, and on school age children to fix protruding ears. Are you thinking about a particular procedure?

Age: It depends on what operation you are talking about. If it is reconstructive in nature than it may be when you are very young. If it is more elective/cosmetic on nature it depends on the surgery but usually at least until they are 18 for informed consent.

It depends.: Plastic surgeons operate on infants, (congenital abnormalities). So it depends on what the patient is looking for. For example, federal regulations say you must wait until 18 for cosmetic breast implants, 22 for silicone. Best to see a board certified plastic surgeon. They will guide you through the process.

Depends on condition: The age will depend on the condition with some surgery performed just before or immediately after birth. In most instances, there is a common recommendation to weight until 10'weeks, 10 pounds , and 10 gms of hemoglobin for semi-elective surgery when a child can better tolerate surgery due to maturation of the immune system. However this greatly varies by area (ears at least 5 years old in usa).