The Biellmann is more a proof of flexibility than a full-fledged element per se, and this is why: it seems to be more about the endpoint and final posture than any sort of innate skating skill. It shows the audience and judges you can grab your foot and pull your leg up backward and that your hips are super flexible. It's like when a cheerleader does the splits. Hooray.
It demonstrates you can keep your pinned ice foot level: if you raise your spinning heel to scrape your toe pick you lose your spin. But like doing the splits you can still show both that you have some control over the process and you can achieve your final pose effortlessly. Pull up your back leg gradually but without struggle, and don't jerk at your stopping top point. If you want to release one hand at the apex okay fine but be graceful and balletic with the free hand.
As far as the static spin posture, the move is so demanding that however your body happens to be ligamented together determines how you will look. Some gals spin more like a tulip flower and others more like a bobby pin; it doesn't appear an individual skater has any leeway over the final positioning of her own hips.
Transitioning out of Biellmann is again the parallel problem of getting up from the splits but with a twist: gravity overcomes your strength in any case. Sigh, the Biellmann.