Main question is if you are legal to fly overhead for a circling assuming you haven’t reached the MAP yet. Asking for visual is another option, but the original question is by staying on the circling procedure. Nevertheless, airport environment is again required to continue.
There is no general prohibition against circling back.
For me is black and white. Flying overhead to position for the downwind you lose the runway once you turn your tail so you are illegal.
For me it is not black and white. I don't see why with 20 - 25° bank you cannot maintain line of sight to the runway environment. To my mind it is legal to circle back. It may not be wise. There is an example in
this article at Fig 4.