It is impossible to unlock all the scenes in a single run, as there are two important paths with their respective scenes (following the romantic route with Emma and being just friends). Anyway, if you use the chapter selector to start from the last chapter, it unlocks all the scenes of the previous chapters. However, the ideal is to play it twice, because although you will be able to see the scenes unlocking them with the chapter selector, there are many things that you will miss.