How to jump back to the base layer of a previous slide and hide last layer shown?

The practice slide can't close a layer on the quiz slide, but the quiz slide can.

One option is on the incorrect layer, if there is a trigger to jump to the practice slide, place a "close this layer" trigger BEFORE the "jump" trigger.

Another method is to set the slide properties on the quiz slide to "Return to initial state on revisit". That will reset everything, so it may not be what you want.