There are a lot of things which should be working, but aren't.
First issue: There seems to be a bug, that you cannot get a endmessage in preview.
So you need to activate the survey to see a endmessage.
Second issue: Hiding the question is not working via the javascript in the helptext.
Use CSS class hidden as shown in the screenshot
Third issue: Piping seems not to work as intended.
Change type of question "Positive" to equation. Just change and save. No need to edit question content itself.
Fourth issue:
Piping seems to work with equation type, but it not transporting everything (embedded javascripts seem to be stripped, haven't investigated)
Is there a reason, why Denis isn't suggesting Expression Manager in the endmessage?
Perhaps there is a issue too, bug when trying to show different content depending on answers my first idea would be using Expression manager in the endmessage.
I have submitted bug reports, but that won't help you now.
bugs.limesurvey.org/view.php?id=13317
bugs.limesurvey.org/view.php?id=13320