If you are working backwards towards a Big Bang singularity, you must inevitably get to a time when no physical laws existed. Nor did space. Nor did time.
"...darkness was over the surface of the deep and the Spirit of God was hovering over the waters. And God said, “Let there be light!”
“[working backwards,] you must inevitably get to a time when no physical laws existed.”
Not necessarily. The laws may exist, the issue is when there is nothing for those laws to apply to. The law of gravity still exists, even if there is no mass for it to act on.