Save action saves the state of all objects on the layout, all variables etc. It doesn't save the game code.
You can exclude some objects (for example static backgrounds, UI elements) from saving by adding NoSave behavior to them.
If you make big changes to your game, saves made in old versions may become incompatible with the new version. If you load such save, the game may not function correctly.
For a word game saving everything is probably not a good idea. I would suggest using LocalStorage to save player's progress only.