At the age of 18 someone can open carry in NV by themselves.
Under 18, persons must be accompanied by an adult while in possession of a firearm unless they are at home, over 14, and have access to an unloadedrifle with permission from a parent.
An 18 year old can be gifted any firearm from a relative. (or buyone from anyone who is not a FFL holder. Rifles can be purchased from FFL holdersbut not pistols at18.) Note that it is illegal to buy a gun specifically for someone else as that would bea straw purchase (there may be some gift exception but I'm not sure how it works). However, someone may buy a gun and then decide to give it to someone. Being 18, I was given a revolver from my parents that they had.
Legal documentation required...not generally. I'm not from Clark County, but it may be that you need to have some paperwork relating to registration in Clark County, since registration is required there.
I would suggest having your drivers license but its not required.