Looking in the mirror my back bend and free leg are about there, but right shoulder is not liking it.
With Biellmann position, it's typically one of three things that challenge the skaters I've worked with:
(1) Opening the hip flexor on the free leg to enable getting the free leg foot to the appropriate height,
(2) Have sufficient strength and flexibility to do the backbend without hinging on your movement segment (a LOT of elites do this incorrectly, but I won't mention any names), and/or
(3) Having sufficient shoulder opening to enable the reach back with both arms to bind (that's the term we use in yoga) the free leg foot.
If #3 is an issue for you, check out the chest/shoulder openers from this simple stretch sequence -- and please note, I'm really a gumby and hyperflexible through my shoulders, so again, practice and patience
HTH