i was playing on 1.8.7 than changed to 1.6.4 and tried to get in my in 1.8.7 made world after that everything was fucked up. when i went back to 1.8.7 i didn't change.
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Looks like your world got corrupted. Could you please add the launcher log?
You can find it in %appdata%\.minecraft\logs
(on Windows)

Dupe of MC-45009. Downgrading is not supported.