Debug mode was in the original game, but it's accessed slightly differently with ResidualVM. You can read more about it here:
It opens up a number of features. Ctrl+G ('Jump to set') is most likely what you want, as it'll let you jump to any scene in the game. You need to be careful here because jumping between scenes can cause obvious issues if, for example, you skip a bunch of scenes where you pick up items that you need during later scenes.
My advice would be to start a new game, then use the 'Jump to set' feature to skip to the beginning of Year 4 — at this point I think
your inventory is cleared anyway and you won't be expected to have talked to anybody by that point, so it shouldn't matter that you've started a new game.