1) How to make new user just see what CC mean?
There is a proverb in English: you can lead a horse to water, but you can't make it drink. code-challenge already has a tag summary which says what it means: there is no way of forcing a new user to read it, to click through for a more detailed explanation, or to think about whether it applies to their case. Perhaps the summary could be improved: if you think so, you can propose new wording for it.
2) What do "hard to solve but win when solved" go?
In most cases, a different website. They break the Q&A model even more than most of our questions. Although the Puzzling site changed its scope to include that kind of question, PPCG has not.
The main exception is programming-puzzle, but that has a very narrow definition, and should ideally have a secondary criterion to pick the best out of multiple solutions.