But even then I see that, when I edit a picture in the copy folder, the original photo is edited as well, even when they have different names.
This is incorrect. The image portion of the original photo is NEVER modified by Lightroom. I don't know what you are looking at, but if you look in Lightroom, it will always display the edited image in the Library Module, even though the image portion of the file on disk has not been modified by even one pixel.
Yes, I know that the original photo is not affected, that's the basis of LR!
What I mean is that when I look in Folder A to picture 5, and I look in Folder B to picture 5, they both display the edits that I made in folder B.
I want to be able to edit pictures in folder B without seeing those modifications in folder A. So that afterwards when I'm done with experimenting, I delete folder B, all edits are gone, and I can begin the serious works with these same pictures in folder A
If the goal is experimenting, why even do it this way? Why try to have two "versions" of the photo in different folders and then struggle with the setup? The much easier way to do this in Lightroom is to import a photo (or use one that has already been imported) and then create a Virtual Copy to experiment on. Then when you are done, delete the virtual copy. This is the way you ought to do this, and is so simple, and your method of using multiple folders is so unclear and complicated that I don't really care to expend my brain power to figure out what you have done with multiple folders. Just do it via virtual copies.