See 17-101 definitions:
12. "LICENSE CLASSIFICATION" MEANS A TYPE OF LICENSE, PERMIT, TAG OR STAMP AUTHORIZED UNDER THIS TITLE AND PRESCRIBED BY THE COMMISSION BY RULE TO TAKE, HANDLE OR POSSESS WILDLIFE.
The commission in rule would prescribe who is eligible for the license, age requirements, what the privileges are etc
As for unlicensed youth because it is simply struck from statute the statute is silent therefore it is permissible (don't need an adult with you). Of course there are other statutes governing firearms and youth that may dictate if a youth can be by themselves with a rifle....,