Phizzy- it was all so simple really. Under cooked Big Macs Ok, a quart of uncle Joe's red Not ok.
2 Cor 11:4 PROVES there were various versions of Jesus and gospels BEFORE the gospels
I do not have a list, but I have seen some Bible commentators say that about 25% of the sayings attributed to Jesus are genuinely his. I recall that one criterion that makes Jesus' words to be considered as genuine is when it is uncomfortable to the Church or unfulfilled. (There is a technical term that I do not recall). In other words, if Jesus said something that is obviously embarrassing to the church, yet they retained it, then it is considered to be genuine. ("This generation will not pass" would qualify, because by the time the story was written - and later included in the 4th century canon - it was clearly a disastrous pronouncement.)
I would appreciate any information if anyone has access to such studies.
One commentator writes that people believe that the words attributed to Jesus are genuine because the words are often written in red colour and the edge of the book has gold leaf applied.
I write about the distance between Paul and Jerusalem in my Study:
A seminal work is "St Paul versus St Peter: A tale of Two Missions", by Michael Goulder, which influenced much of John Shelby Spong's writings.