Did not see the "alone" part in the first post. The third post just asked for a minimum age which I supplied. Try this tidbit I found on the same NJDEP website.
Youth Licenses
Properly licensed youth hunters (resident & non-resident) aged 10–13 may hunt only when accompanied by a properly licensed adult aged 21 or older. Youths, 15 years of age and under, are able to hunt and trap for free, provided they have passed a
Hunter Education course.
Youth Licenses are valid from time of issuance until end of the year the holder turns 16. More information is available on the
Youth License page.