Summoner names of champions?

Hey guys, I'm just wondering if it's possible to change your summoner name to the name of an in game champion. I was interested in this so I started looking up the profile of xin zao, annie, ahri, vi... ect. I noticed that all these accounts are level 6 that don't have a match history. Does riot have it like this so people can't get these names or does somebody have all of these accounts?

If someone has all these accounts how do they keep them for being inactive for so long? I thought that after 6 moths of inactivity (at level 6) that the names would become available. Does anyone have extra information on this?