The default buttons of Construct2 are very limited, if its not wanting to cooperate, I would recommend making your own sprite button and simply writing your own control events for when the sprite is clicked on, hovered over, etc. This will allow you to use all the cool sprite actions as well.
That said, have you tried simply setting the other buttons invisible during this period (and then spawning fake ones that do nothing), or overlaying them with an invisible sprite on another higher clear layer so they can't be clicked, or giving each a variable condition you can toggle on/off when play is active...