Advance a Slide After Objects Have Been Viewed

I have blogged a similar solution many times, with the difference that the action when all Boolean variables were toggled to 1, a Next button would appear, but you can replace that command Show, by Go to Next slide.

To avoid having the create all those user variables, I usually use a shared acton which I drag from an external library to the project library, one of the tricks in this blog post:

http://blog.lilybiri.com/rare-tips-for-shared-actions

Here is what I would do.

I would create variables for each of the 8 objects such as obj1, obj2, etc, as appropriate. I would also include a total variable that sums the eight of them.
When the learner clicks on each one - the value of that variable changes from 0 to 1.

Since you are always coming back to this landing slide - make an onEnter action to check the variable such that when we come back to the landing slide - if the total is eight they can jump to whatever slide or if it isn't equal to eight we do nothing and stay on that slide.

Hopefully that quick rundown makes sense and addresses your question.