mountain edge biome will NOT spawn under normal world, only in Buffet world type.
cave update is pushed backed starting from 21w15a
The same goes for the caves biomes
IF you want to experiment with the new features the Mojang will release in 1.18,
use the datapack provided here:https://launcher.mojang.com/v1/objects/622bf0fd298e1e164ecd05d866045ed5941283cf/CavesAndCliffsPreview.zip
note*piz do not mark unreleased version,you don't have access to the game version.
because the time is almost night that why is look dark. everything is normal.
this is a game design
duplicate of MC-227996