Some Korean children's parents will let them trim their hair when they are about ten years old.

If you are an artist, you don't usually have plastic surgery before you debut. If the company chooses you to debut, it will naturally arrange a positioning for you, and then go for plastic surgery or micro-plastic surgery according to the positioning.

So the youngest should be 10 years old.

(My sister, her primary school classmate is Korean, 1 1 year old, and has been rectified twice. )