Will Elderkin

So what is the issue? Those 3 buttons are intentional

When you respawn the dragon, the structures, like the exit portal the End pillars and when you enter the end regenerate to what they are supposed to be, removing blocks in the structure or touching.

In hard mode, the wither effect lasts for 40 seconds, not 10 like on normal.

Whilr this is sort of cheating, try a X ray glitch, it helps find caves and other air pockets under ground, but even more annoying is where you find a stronghold with no portal room, not even when digging around

The Terrain generates things like that, a Lily of the Valley was there, then Minecraft put a river there, putting sand under, but not updating the flower, If you update it, It will break