While I agree with the sentiment here, Penrose has come up with a model that does make testable hypotheses about what happened before the big bang with his Conformal Cyclic Cosmology. Now, I think that as a matter of fact, the predictions he made have turned out to not be true, but at least he came up with a way to test them. If I recall correctly, the predictions had to do with patterns in the CMB that would have been left over from black holes in a universe before the big bang, and those patterns ended up not being there. It wasn't the right answer, but that's science.
There are no experiments one can do to empirically test things asserted before the Big Bang.