A:
I don't believe laminate manufacturers recommend installing laminate over hardwood flooring. Is your hardwood in such bad shape that it could not be properly sanded and finished?
That aside, how much of a dip are we talking about here? If it is not too severe, you could use building paper to build up the dip. However, if it is a hump, you have a bigger problem.
A: I have never read a spec on not using osb as a sub floor for laminates. I have read that they (or some versions of them) are ok for nail down also, but I still prefer real wood plywood. You should be fine.

