As I imported the folder with all my photos from one computer to another, the edited pictures are read by lightroom as the originals, meaning that in the "before/after" developer mode, the edited picture appear as both before and after. I can reset the settings of the image and the "before" image stays with the edits. I would appreciate any help in indicating lightroom to choose the original image instead of the edited one.
As I imported the folder with all my photos from one computer to another,
This would seem to be the start of the problem. Importing a second time is virtually never a good idea. See this link for correctly moving LR from one computer to another: