Can't play on lower versions than 1.13

(BTW at affected versions I can only write 1.15.1, so don't look at that)
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I was playing on the highest version(1.15.1), because once a new version appeared, my launcher updated to it. But, one day, I wanted to play on a server that required 1.8. When I try to play, it says that the game has unexpectedly crashed. bruh.
Now, I thought versions lower than 1.15.1, but I tried, and apparently the versions above 1.12.2 I can play, but lower than 1.12.1 I can't. But for 1.12.1 and 1.12.2 I'm still waiting to load.
That's all.
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EDIT: 1.12.1 and 1.12.2 never loaded.