Who is depicted in this sculpture? Also, what are her feet resting on?
This is a sculpture of Wadjet, a powerful lion headed goddess. The sculpture functioned as a coffin for a mummified ichneumon (Egyptian mongoose) and would have been placed in a temple. Many ancient Egyptian seated statues show a platform under the feet; sometimes it serves as a place for inscription.
What are the symbols on her arm? What is she wearing on her head?
I believe she is wearing an arm band, which is decorative jewelry for elite and divine subjects in Ancient Egypt. And it's probable that on her head was a sun disk, meant to show her divine status and her relationship (as daugher) to the sun god Re. This looks to be broken off and we are just left with a remnant.
Is that jewelry displayed around her hands too?
Yes, they are also decorated with bracelets. The more lavish and detailed the decorations on a divine figure, the more important they were considered in the hierarchy of the gods.
Is she sitting on a throne?
Yes, she is. You'll see different kinds of styling for thrones throughout the galleries. Styles changed throughout the dynasties, sometimes there were innovations, sometimes artists of a later dynasty would start reusing styles from an earlier period (called archaism) to associate their time with the positive attributes of an earlier generation.
Why would they create human and animal features in the face?
Most ancient Egyptian deities were associated with an animal and its attributes. They were all commonly shown with a human body and the head of the animal. This easily communicated that it was the deity and not just the animal, for example.
Thank you so much for your help. This is such a useful resource!