Invulnerable?
Is it possible that using Immortality Rings and Gorgeouspil for hundreds or thousands years, human body will become invulnerable, because of extremely dense cells and tissues?

I don't think anybody will ever have to worry about that.

dense cells and tissues won't make you invulnerable you can still get viruses and diseases from eating bad food most animals can too, besides vultures they can eat anything almost anything.