Extreme Glitches in UI and Textures

Upon loading the game, the menu is extremely bugged out (though still functional.) Continuing from the menu into the game shows that the game itself is incredibly bugged as a whole on the visuals.

I wasn't able to get screenshots of the mobs, but they would continuously flicker between the textures of all sorts of mobs. A villager could flicker between a whole bunch of other villager textures in just a few seconds, turn invisible, or even have a different mob's texture stretched onto it (such as a horse). This would happen with all mobs, like cows flickering to creeper textures and so on, with every mob I saw.

The screenshots below explain how everything else broke pretty well.