Its fixed, closing my question

@leocg about extensions - yes,
but profile i didnt touch

Youtube started working incorrect spontaneously, I did not go into the settings before this incident. I doubt that such drastic measures will have any effect other than wasting my time

@leocg Yes, and as i say - i not enabled auto-clear cookies

YouTube dont save black theme and turned off auto-play, auto-clear cookies is turned off