Option (1) is correct: For a valid adoption, if the adoption is by a female and the person to be adopted is a male, the adoptive mother should be at least 21 years older than the person to be adopted.
Option (2) is incorrect: The adoption is not voidable at the instance of boy.
Option (3) is incorrect: The adoption is immoral and not enforceable.
Option (4) is incorrect: Completely void.