Firescale, Pickle and CZ

I have a size reduction repair to a sterling shanked ring with a
large CZ stone.

  1. Can the CZ safely be placed in Boric Acid?

  2. To remove the firescale protection, can the CZ go into pickle or
    how can it be removed?

  3. I understand I can heat protect the CZ in KoolJool or water and
    just treat the shank but, I would like to understand the possible
    effects, if any, on the CZ if “normal” processes are used including
    Boric Acid and Pickle.