if conditionals (maybe) Giving a user 3 out of 12 chance when selecting buttons

I'm a complete novice when it comes to HTML5 actions and I'd really like some help trying to figure out a very specific issue if you would?

I have 12 squares (buttons), each button pulls a single random answer from a pot of 12. Each time a single button is selected and the answer is shown the button disappears. So far I have all this working.

The next step is that I want the user to only be able to choose 3 of the 12 buttons - any three, entirely at random and when the 3 have been selected the rest become inactive.

Any help you can provide would really help me,

(by the way I work through Adobe Animate CC)

Thanks,

Aidan