Laurent - you're selecting play with the export format set to Twison. That's the method that you use to obtain the JSON export from Twine, but if you want to run through it in your browser then you need to select the export format inside the Instructions story.
Here's how to do it. With Instructions open as the active story, select "Instructions" popup by the home button (bottom left - the popup name is the same as the project story name) then select "Change Story Format" and select something that is not Twison (I recommend "Harlowe"). Et voila! I hope. Let me know if that works - but the text you pasted above is the Twison export, so I am sure that these steps will help.