There are 3 different difficulty modes - easy, normal and hard. You can adjust the mode in the addon settings with the little gear.
I recommend not to change the mode after you started the challenge, because this can break the functionality.

At the beginning you will get some "start items" (not in hard mode):

Modes:

• Easy
  15-20 minutes at the beginning and between the instructions (the block on which you have to stand)
  10 minutes time to get the right block
• Normal
  10-15 minutes at the beginning and between the instructions (the block on which you have to stand)
  5 minutes time to get the right block
• Hard
  3-7 minutes at the beginning and between the instructions (the block on which you have to stand)
  4 minutes time to get the right block

other information:

While the last 10 seconds there will be a countdown and at the latest then you should stand on the block. If it is the right block you can go on with the challange in this world and you have 15-20/10-15/3-7 (depending on the mode) minutes again until you will get the next instruction. But if you didn`t get the right block or it is not the right block or you don`t stand at the right time on the block, you will be "killed" and set to gamemode spectator permanently. This means you can`t play in this world anymore and you must try the challenge in a new world (or you can spectate the other player(s) if you play in multiplayer).
In multiplayer every player gets a different block. If a player leaves the world while there is an instruction, the timer for this player stops (for all other players it goes on). And if the player joins again later, the timer continues and for all players who have no instruction anymore the timer between the instructions stops untill the player passed the instruction (or not and is a spectator now).

Which block you get (for every player different, 155 possible blocks) and the time between the instructions (for every player the same, 15-20/10-15/3-7 minutes, but you don't know how many minutes it is) are completely random.
Only in the easy mode the chance to get an easier block is a bit higher.
 

for example:

or

I hope you have fun and it is not too easy 🙂