This Sky Block can be played only with Ex Nihilo mod because there is no resources provided in chest for vanilla survival,
there is only bucket of lava and 2 ice in starting chest which is enough for Ex Nihilo survival.
There is two different downloads, you can play map with large tree or small tree (if you played skyblock maps before you probably know that small trees sometimes don't drop sapling).
I didn't put mushrooms in chest cause you can find them in nether.
Also, nether is not edited, if you create nether portal it will give you regular nether from vanilla minecraft.
File is zipped so to install it corectly you need to unzip it with winrar or similar program and just drag it into "saves" folder.