Help with variable and conditions for 2 sets of slide navigation

We have built the attached with two scenes. We have set the player to 'free navigation' so that learners can go straight to the scenarios if they want. The difficulty we are having is with the slide in the first scene. We want learners who are just going through slide by slide (e.g. if we had 15-20 slides in the first scene) in a linear way - they can just press next slide - that's fine.

The other group of learners will only visit this slide in the first scene, if they answer a question incorrectly in the second scene - adding a jump to slide trigger on the incorrect slide layer is fine too.

I have read through a lot of articles and posts - it does not appear that you can assign two types to the Player next button and suggestions are to put in a custom button. However we have not been able to make this work either because we don't know how to write a true/false variable that says - if you have come from slide Qu1 - on 'next' , go back to Qu1 whilst at the same time, have a trigger for the learners who have not been to the question scenarios to go onto the next slide.

It's how to indicate the concept of slide previously visited (and Articulate Storyline must somewhere know what this is otherwise it would not know how to prompt learners when they revisit a course to say - would you like to start from where you previously where?)

Another alternative is to keep the next Player button showing for the learners going through slide by slide and then for the second set of learners, have a custom button, but don't know how to write a variable to say if you have not come from slide Qu1 this should be hidden (maybe as a true/false variable? )

Any ideas?