Reset app/game so I can play again, resetting app state to initial state

I am making a memory game where images are shown randomly. When shown twice they are removed from the list. How do I reset the list so player can restart?

How I set it up. Data type: Image path and integer (shown count) This is used to create app state list of the two and when image is presented shown count increases +1. When shown count = 2 image is removed from list.

Data is not persisted. When I reload test mode I can play again. But I want to have a button doing the same. I made a button to go back and start over but get error because no items in my list.

Update app state>clear value does not work.