The first part is a matter of probabilities. It’s very unlikely by virtue of the sheer number of possible configurations vs how many times a deck is shuffled in history (even erring on the high side)

For the second part, the composition of elements in most stars is known. And the total mass of the universe is approximated by observing gravitational effects. Which is what you need to work out approx number of atoms.

It’s only in a statistical sense. Combinations based off a few shuffles from a standard sorted deck would be fairly common in practice.