IS there a way to hide the created at and the modified at lines that appear when editing or previewing an item on a list? I want this changes to be kind of anonymous
You could remove the info from the DOM with script, but it would still be there for a second as the page loads.
You could also customize the form and simply not show that information, which would be more "secure".
Finally, custom development, but that seems like overkill for your goal.