The only admissible one is “Que se passe-t-il ?” (note the addition of a hyphen between passe and t)

• “Que veut dire ?” is not correct (it is equivalent to “What means?”)

  The correct form would be “Que veut dire… ?” (“What does … mean?”)

• “Qu’est-ce qui veut dire apothéose ?” is not correct either (“What does it mean apothéose?”)

  You should use “Que veut dire apothéose ?”

• “Qu’y attire ?” → “What appeals to?”

  Try “Qu’est-ce qui vous attire ?” instead (“What appeals to you?”)

By the way, this is not correct: “Qu’est-ce qui vous y attirez ?”

It should be “Qu’est-ce qui vous y attire ?” (What appeals to you about it, what attracts you to it) because the subject of attire is qui, not vous.