Visited States

Based on what I see in Review 360, here's what I suggest:

Don't use hotspots. Instead, have the desired triggers run when the user clicks the labels. Because you already gave those a Visited state, each one will change automatically to Visited when clicked. In other words, the labels are your buttons.

When the user doesn't leave the slide, you can use the objects reaching the Visited state as the "when" in a trigger. Here's an example:

When the user jumps to other slides and then returns to the slide with the buttons, use a "when the timeline starts on this slide" trigger with conditions to control the Next button. Here's an example:

• Notice that the conditions are connected with "or." That means the action will be performed (e.g., Next will be disabled) if any condition is met.
• A "when the timeline starts on this slide" trigger will run every time the user visits a slide. That's true even if the Slide Properties are set to "Resume saved state." 

For additional info:

• TIP: Controlling the NEXT Button 101 | Articulate - Community
• TIP: Create a Custom Menu Slide | Articulate - Community 
• PRIMER: Hotspots vs. Transparent Shapes | Articulate - Community (for when there aren't separate labels or other objects for the user to click)