One can reject a wrong doctrine and still not be a Christian.
They must accept Christ as anyone must.
The law was put in charge to lead us to Christ. It’s about Him, not about anything or anyone else.
The Pope is merely the leader of the Roman Catholic Church. He has no authority over any other denominations and likely they don’t recognize the claims made by Catholics of his divine appointment.
Your appealing to the Pope means something only to Catholics. To the rest of us he’s just a man holding an important position of leadership.