It is a non-linear map which have many paths to take and reach the end. The point is, that you play a map one time and you are happy. Then you have a little break in Portal, because there aren't any new released maps for some time. But the answer is here: play the Deja-Vu again, but choose a different path with different puzzles. You can choose freely the way that is going to lead you to the end. Thats it!
(2023.7.19 update: change game to Portal: Prelude RTX) Add RTX support for Aperture : Déjà vu mod.(Patches included!)
Patches included...