Buttons interaction accessibility

It really depends on how the interaction works.

If you have buttons that open layers and the layers are like popups and have a close button then you should set each layer property to prevent user from clicking on the base layer. Doing this the user will click a button the focus will switch to the layer and cycle through in the order on the focus order and then when you press close it will jump back to the previously selected button. 

If however it is more a tabbed interaction without a close button then you shouldn't prevent user clicking on the base layer, but in the focus order ensure each layer is after its corresponding button and then the focus order will go, button, layer content, next button, etc...

If you hide the objects on the base layer there is a possibility that each time you return to the base layer it starts reading from the beginning (In never use this option so have not tested)