I thought the questioning(sorry) oswin wouldnt change the story(or game) but it did it added choice in specific scene
Still hints on Oz questions... don't read this if you still want to guess them by yourself...
Usually short words work, but sometimes you need to insert a longer phrase to be answered...
You can ask different things to him... the only word (in my experience) which added something to the story, though, was rabbits.
If you never tried, you can also insert the question: can you tell me a story, to hear an alternate version of Hansel & Gretel.
You can ask about benson, micology, secret passageways, the vault, the shack in the woods, medals, microphones (or cameras, it's the same) and probably other stuff... but this is all that I've found (if memory doesn't fail me) till now.