Question for Google Analytics experts

So I have a wordpress site.

I want to run an experience that tests 3 different landing pages.

I added the experiment code to the "original" LP (at the very top), but it doesn't work (error message)

I add the variable codes to the two other LPs which works (recognized by Google)

So then I add the experiment code to my Themes header.php, and Google recognizes it (deleted it from the page itself).

But I don't think it is working. One problem is that I visited my website from different computers several times and only the original LP shows. Secondly, I see a long string after the URL in the browser window related to the code, which doesn't look right (looks a bit scary actually).

These results are with the WP Read settings Make Front Page a Static Page (set to the Original LP).

Then, I changed it back to Make Front Page your Recent Posts. Now, I don't get any of the LPs when I visit my site multiple times, and that long ugly string is in the browser windows.

Has anyone set up such an experiment on a Word Press site successfully? What am I doing wrong?

Thanks for any help.