Cathy Munsch is immortal. When the girl in the bathtub die and to 2015 she seem to does not age at all. She demonstrated that she can survive from poisons/toxins, and coldest climates. Immortality is very possible for her
It is probably that the RD saved Dean Munsch because the RD wants to know Sophia Doyle's resting place. No one knows except Dean Munsch.
The RD (which could be one of the Kappa), switched the apple cider and maybe hacked into the cyotherapy giving it only low temperature, fooling everyone.
The temperature was probably -10 or -20 something not -200. The machine was rigged. -10 still show some elements of freezing.
I was about to correct you on "an" and other mistakes, then I realized English isn't your first language, and it would've been mean. Also, this isn't YouTube.
She learned intense meditation techniques to keep her core body temperature above freezing from the same lover who taught her martial arts.
Or she drink Marie Laveau's tears
What do you think?