jc57 provided the proper source documentation. Here's the lay-person explanation:
There are no specific laws regarding knives that apply to minors. You follow the same rules that everyone else does. There are two exceptions: Local ordinances, and the right of a store to refuse selling to a minor.
It is legal to carry most knives openly, but illegal to carry any knife other than a "common pocket knife" concealed. What is a common pocket knife? While no definition is provided in the statute, case law has established that it's a folding knife that isn't overtly weapon like. Thus it should have a blade less than 4" and not have a bunch of "tactical" features. The knife you mentioned may actually run afoul of that, since it's appearance suggests it is intended to be a weapon. A knife can also cross over into illegal if it is used or carried during the commission of a crime.
In general, knives are not good self-defense weapons. They do have their place and they can be effective in narrow circumstances, but only when carried correctly so that it is readily accessible under stress, by someone with some reasonable understanding of not only how to use one, but an understanding of how self-defense law works. That is, that use of a knife is a considered deadly force, and therefore will be considered excessive force/aggravated assault if used inappropriately (for example against an attacker who is unarmed and/or when there is an avenue of escape).