The Dink Network

In the green caves, when you go to save baby Roland, you can see (but not get to) an elixer in an area that also leads to a light sword. Now I know this in part bacause of the warp function of the cheat (ahem, I heard about it from someone, somewhere). In the walkthrough, SimonK suggests that I could access this legally by bombing something earlier. So, two questions:

1. What is that something? (I've "talked to" everything that looks bombable, I think.)

2. Is is safe to assume that, once Roland is saved and the original entrance to the green cave sealed, one can no longer bomb one's way back to that light sword?

Thanks.