Limiting the number of selections a user can make on custom buttons

The attached sample will do what you are asking. I made the changes only to slide 1.2.

But if I could barge in with some unsolicited advice, I would make one serious change. Showing more detail and giving credit for making a selection really needs to be a more deliberate action. As it is, if the learner comes to this slide with their cursor at the top of the page, and wants to select an option at the bottom of the list, it is quite likely they will move the cursor across the whole list, and inadvertently make four selections, instead of the one they intended. I would strongly suggest showing the layer when the learner clicks, then on the layer, having a clickable object to hide the layer.

Either way, the attached version allows only five hovers, prevents multiple hovers on one object, and changes the state of the objects when once hovered over. If you change the triggers that show the layers from hover to click, it will still work the same.