Like all their man made doctrines, it's not from God. So the Vatican will define it however they want and will apply it however/whenever they want to suite their agenda.
The concept of any man having “infallibility” - is pagan, warped and laughable.
God is The Almighty One and Supreme over ALL.
Yes, and He speaks to us infallibly through His Church, its Magisterium, and its Popes, all of whom conspired with the Holy Spirit to produce the Sacred Scriptures.