I can not see an option to disable that in the new Developers design!
Its seems they have moved this option to the "Status & Review" section. When accessing this section you will see this text: Do you want to make this app and all its live features available to the general public? And a button where you can change it to "Yes" or "No".
before go to the "Status & Review" option, first you need to go to settings option and add "Contact Email", then go to "Status & Review" When accessing this section you will see this text: Do you want to make this app and all its live features available to the general public? And a button where you can change it to "Yes" or "No".
Our app went to the sandbox mode automatically after a while. We had to fill the 'privacy policy' url, after that we could disable sandbox mode again.
So make sure you have everything filled in correctly.
Y Solved it in Settings-->Contact Email: type it. Then go to Status & Review and put it on the Do you want to make this app and all its live features available to the general public? option at top of the page.
Also make sure that the age restrictions +13 and country is not set.
来源：https://stackoverflow.com/questions/20706322/how-to-disable-sandbox-mode-for-app-in-new-facebook-developer