To apply for V-2 status, you must:
The V-2 or V-3 status is valid only up to the 21st birthday. If when initially admitted from abroad, or granted change of status in the U.S., the child is at least 19 years old, the status will be given only until the 21st birthday, rather than for the standard two-year period.
If the child turns 21, then the immigrant petition converts to the 2B category. While the I-130 petition remains valid, the V status terminates and the child will either have to leave the U.S. or change to some other nonimmigrant status for which the child may qualify, depending upon the circumstances.
If the V-2 or V-3 child marries, then both the immigrant petition and the V status terminate as Lawful Permanent Residents cannot petition for their married children.