Is the Prophet infallible from every sin, or only from major sins? And is doubting the Prophet's bravery in comparison to 'Umar considered disbelief, and what are the situations that demonstrate the Prophet's bravery?

Prophets are infallible regarding major sins by consensus of the Ummah, but scholars differ on their infallibility regarding minor sins. Prophets are not left to persist in error, nor do they delay repentance from it. No sane person doubts the courage of the Prophet, peace and blessings be upon him, for he was the bravest of people in difficult situations, and the Companions would seek protection behind him when the battle intensified. What a person finds within himself of feelings carries no sin unless he speaks or acts upon them.