I can not look at my commands in game is gives me a error message everytime.. and do you get anything for completing them in 2.1?
Not entirely sure if it has been added, although I'm pretty sure it hasn't -- this is a custom SkyBlock plugin, so there is no /c command (If that is the command you are talking about).
If you're looking for simple commands (/warp, /coop invite ect) Then type /help. As so2315 said, there is no such thing as a challenge command sorry.