Accessing CSV from a Google Docs Spreadsheet

I try to access a Google Docs Spreadsheet, so I can use it in a D3.js visualization. Both

• https://docs.google.com/spreadsheets/d/1s04t-0r5dtY4c31czCGCaxRS_nbAMDmoUJ5O75leGPE/export?format=csv&id (as in Accessing google docs spreadsheet revisited in 2014)
• http://docs.google.com/feeds/download/spreadsheets/Export?key=1s04t-0r5dtY4c31czCGCaxRS_nbAMDmoUJ5O75leGPE&exportFormat=csv&gid=0 (as in Using the google drive API to download a spreadsheet in csv format)

do work for downloading the data, but not for using them for other websites, as I am getting an error No 'Access-Control-Allow-Origin' header is present on the requested resource.

However, an approach that should work (Download unpublished Google spreadsheet as CSV, see also this post):

• https://docs.google.com/spreadsheet/ccc?key=1s04t-0r5dtY4c31czCGCaxRS_nbAMDmoUJ5O75leGPE&output=csv&gid=0

does not work at all (redirect to typical edit view).

For another variant, used by http://christopheviau.com/d3list/gallery.html:

• https://docs.google.com/spreadsheet/pub?key=0AqMEGBUNwXeHdHpQNlVuY29SUE5BSXVtS3JueGlNYVE&single=true&gid=0&output=csv

I cannot do the same with my code (changing keys results in an error: Sorry, the file you have requested does not exist.).

What I am doing wrong?