Is ModSkin app Prohibited?

i wanted to ask before even thinking about using this app because i really care about my account and have been progressing through it for 3 years and still am. I wanted to check if an app which allows me to try out any skin for free is allowed in LOL terms. Its not that it affects anything in game or any other players, it just allows me to try out some skins for free and i only get to see them ofcourse. Nobody can see the skin except myself. The app doesn't affect anything in game or changes anything. It just allows me to tryout skins to check if they are worth buying or not and satisfies me in playing the game even more. So? is it allowed? or i may get banned?
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