Showing/hiding in advanced actions

Here's a problem I'm having. In a drop-down widget, I ask users to choose their native language (ex. Japanese, Spanish, Arabic) and click submit.

The "language" is assigned to a variable, and through advanced actions, depending on that variable value, some buttons are shown on screen.

If the user then changes the language and submits, new buttons should be shown and some previous buttons might be hidden.

How can I reset the variable to "0" before the new value is assigned - in one click?  In other words - previous buttons are hidden, and only new ones appear.

I don't want to add a separate "clear" button because it will be confusing - users might think they're clearing a different kind of selection I have.

In advanced actions, I could set something like:

if var_lang = Japanese,  show buttons A and B but hide buttons C,D,E,F,G,H,...

if var_lang = Korean, show buttons B and D, but hide buttons B,C,E,F....

etc.

But this is really laborious. 

One solution would be to replicate the slide.  Then when the user clicks submit, hide all buttons and assign the var_lang value, and go to next slide. On entering the next slide, the advanced action would show buttons conditional to the var_lang. And so every time the user changes language, he she will jump back and forth between the two slides.  But it would be better if the user could stay on the same slide.

Is there a better way to do this?  Thank you.