>Do you have any idea how hard that is to actually do?
She gets a lot of practice... but really yeah it's physically impossible the way it's depicted here - unless his cock takes a 90 degree bend or enters her brain stem.
>Any chance this animation will ever be sketched out the rest of the way?
Maybe. There's a looped version where her arms and hair don't disappear in the upload queue.
Is she trying to get her tongue on his balls 'cuz her master taunted her to lick them, and she wanted to prove to him that she was up to the challenge?