“Protestantism does not have a singular belief.”
Doctrinally? Of course it does.
Individually? Common to every worshipper? No. Neither does the Catholic denomination.
Wrong. Catholic Church has a Credo and a Catechism
The only common Protestant “doctrine” is:
John 3:16 and hate Catholics.
And then they go on to tell you that the Holy Spirit will guide each of you individually, but the Holy Spirit does not guide the Pope with a single truth.