UPDATE
I know what's going on. There are infinite of every block in the world.
Also, breaking a furnace in the world crashes the game and breaking redstone makes its brightness go to off and scroll-clicking the double slab blocks gets mostly tile.stoneSlab.slabName.name such as tile.stoneSlab.cobblestone.name and the wood slabs texture is a purple and black checkerboard and a=has the name tile.stoneSlab.wood_old.name.
Also, summoning PrimedTnt near the two TNT blocks (what's the difference between them?) creates endless TNT (lol). Good thing my computer's so powerful

Walking into one of the pressure plates in the Test world Throws up tons of items, creates game-stopping lag and causes Minecraft to stop responding; so badly that I alt+tab then close the game externally. I'm pretty sure pressure plates shouldn't throw up that many items.
The screenshot shows what happened when I threw an item into it (the screen is gray as Minecraft stopped responding)
The same thing happens with stone pressure plates.