The only thing pertaining to salvation is faith in Christ alone for salvation. That cannot be changed or amended.
The church cannot change what is sin and what is not. God established that Himself. The church claiming that it has that power is usurping God’s authority and putting itself above God.
What blasphemy.
Depends on the nature of the purported sin. Eating pork or not circumcising boys were sins till the Church abolished these restrictions (Acts 15).
Ceremonial and disciplinary law is the prerogative of the Church. Laws of faith, nature and ethics are different, -- the Church may clarify them but she will not fundamentally change them.