https://www.leagueoflegends.com/ko-kr/news/dev/dev-league-of-legends-classic/
According to this, "Classic skins can be unlocked using Classic Skin Tokens, which can be obtained through the Season Pass (including both free and paid tracks) or the shop. Tokens alone can purchase all Classic skins, and if a skin for your main champion hasn't been released yet, you can save your tokens for later." is written there.
Probably because it's the test server.
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but you should only use those musty old skins from back then, i don't get why current skins are allowed
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But besides that, there are quite a few things that are too low fidelity to be called classic (like the systems, etc.), so overall it's just too disappointing compared to what I expected
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