That's not how mRNA works; the whole point is that it temporarily induces some cells to produce spike protein, but this effect does not last long as mRNA by its nature decays as it is used.

Also, that's not what autoimmune means.

Also, there were not "deaths of all animals" or even some; you can read about Pfizer's initial animal testing here: https://www.biorxiv.org/content/10.1101/2020.09.08.280818v1.... and the results here: https://www.fda.gov/media/144416/download There's also a follow-up paper here: https://www.nature.com/articles/s41586-021-03275-y