With the apple challenge, his point was that, if something was created
ex nihilo, there's little you can do to prove it. Thus, asking for evidence for Creation is a doomed endeavour, as there
can't be any evidence: creation
ex nihilo, like the apple
ex nihilo, leaves no footprints. More or less.
With the bike challenge, he has this idea that the Earth is both 6000 years old and 4.5 billion years old. When pushed, he said that the Earth has gone round the Sun about 6000 times, and the '4.5 billion' figure is 'embedded history'. While this may sound a lot like the Omphalos defence - God made the world
look like it's very old, but in reality it's very young - but he assures us that it is not. The bike challenge, then, could well be his way of trying to explain the difference between 'real' and 'embedded' age.
Or I could be way off on both counts. I've been here a while, and I still don't know