The goal is to have the feet on the floor next to the body. Then one can work on opening the chest because there is stability. Trying to bent backward in this pose feels a bit awkward. It's good to lift the knees higher. It stretches the muscles of the legs.
This is the exercises that I do before bhekasana when I practice at home. I sit between 2 blocks, then I put my feet on it and lie down. I recommend to do this exercise with a lot of care. As soon as the knees hurt one must stop doing it. Yet one can also feel a sensation on the muscles of the legs and this is wished. This exercise helps me to get deeper into the pose called bhekasana.