It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

I wanna say that when launching the game, it goes always on the same false monitor (for me).

Whereas you try to change de default screen, the order of monitors (left to right), etc...
The result is always the same: the game is launching on the bad monitor (16:9 for me whereas i wanna play on the 4:3 one).

The only solution: disconnect the screen in windows!... :(