If what are you saying it's true and you're actually playing the alpha 0.2.0 #8 we can assume that the skip button is unlocked only once you have beat the challenge at least once, as I have done.
Anyway beat the challange it's not difficult.
The first thing you really wanna do is to set your controls to be easy to press.
I use a combination of the left/right arrows and the 4/6 keys from the numpad.
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Then you can start the challange.
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Your goal is to keep the black bar out of the red area using the selected keys.
Every time you leave it in the red area your "cum" meter on the left will increase, and if it reach the full status you will lost.
If you manage to keep the black bar inside the white area you will not gain any penality and if you manage to place in the green zone your com meter will be reset.
Easy peasy. Enjoy.