Levonorgestrel and Estradiol?

If that child is sexually active and has started having periods then if a doctor orders the MAP for them it is OK to take.

For emergency contraceptive purposes, the contraindications are allergy to its components, age before first period, age more than one year after last period, and pregnancy (for which it won't work).

Yes, it can prevent a pregnancy.

A semi-synthetic derivative of estradiol--an estrogen or female sex hormone--used in birth control pills and combined ECPs

Levonorgestrel is an artificial progesterone used for contraception, both in traditional combined oral contraceptives, in progestin-only pills, and in emergency contraceptive pills.