One more suggestion in the attached Random12.xlsx
The random function in XLSForm generates random numbers. For example: int(12*random())+1 will generate a number between 1 and 12 (included). You can then use that number to show/hide questions.
With the logic in the attached XLSForm, there is a small chance you could potentially get fewer than 3 questions if random picks the same number twice. I added a simple check, but it is not bullet proof.