At least that part is correct. What is God's will?
Don't forget Ephesians 4:5. A church that doesn't baptize isn't the Church of Jesus Christ.
As a side question: the real First Corinthians is discovered. Does it become canon, why or why not?
It is not possible for a human to conceive all of God’s will. We can only perceive what God’s will is for our own lives. By the leading of the Holy Spirit and reading the word are we able to apply those influences to first understand our situation and then apply those leading and teachings to our choices.
A church that worships prosperity (or any other doctrine) isn’t a church of Jesus.
That depends on what is found in the book. Does it align with the current New Testament? Are there any false doctrines contained within text? Can the authenticity be verified? If there are no problems, why not?