http://www.carm.org/manuscript-evidence
Also this is referred to in the Latin as Pericope Adulterae:
The pericope is not found in its canonical place in any of the earliest surviving Greek Gospel manuscripts; neither in the two 3rd century papyrus witnesses to John - P66 and P75; nor in the 4th century Codex Sinaiticus and Vaticanus, although all four of these manuscripts may acknowledge the existence of the passage via diacritical marks at the spot. The first surviving Greek manuscript to contain the pericope is the Latin/Greek diglot Codex Bezae of the late 4th or early 5th century. Papias (circa AD 125) refers to a story of Jesus and a woman "accused of many sins" as being found in the Gospel of the Hebrews, which may well refer to this passage; there is a very certain quotation of the pericope adulterae in the 3rd Century Syriac Didascalia Apostolorum; though without indicating John's Gospel. The Constitutions of the Holy Apostles Book II.24 refers to the passage “And when the elders had set another woman who had sinned before Him, and had left the sentence to Him, and were gone out, our Lord, the Searcher of the hearts, inquiring of her whether the elders had condemned her, and being answered No, He said unto her: “Go thy way therefore, for neither do I condemn thee.” Book II is generally dated to the late third century (Von Drey, Krabbe, Bunsen, Funk). Codex Fuldensis, which is positively dated to AD 546 contains the adulterae pericope. The Second Epistle of Pope Callistus section 6 contains a quote that may be from John 8:11 - "Let him see to it that he sin no more, that the sentence of the Gospel may abide in him: “Go, and sin no more.”" However the epistle quotes from eighth century writings and is not thought to be genuine.
Until recently, it was not thought that any Greek Church Father had taken note of the passage before the 12th Century; but in 1941 a large collection of the writings of Didymus the Blind (ca. 313- 398) was discovered in Egypt, including a reference to the pericope adulterae as being found in "several copies"; and it is now considered established that this passage was present in its canonical place in many Greek manuscripts known in Alexandria and elsewhere from the 4th Century onwards. In support of this it is noted that the 4th century Codex Vaticanus, which was written in Egypt, marks the end of John chapter 7 with an "umlaut", indicating that an alternative reading was known at this point. Jerome reports that the pericope adulterae was to be found in its canonical place in "many Greek and Latin manuscripts" in Rome and the Latin West in the late 4th Century. This is confirmed by the consensus of Latin Fathers of the 4th and 5th Centuries CE; including Ambrose, and Augustine. The latter claimed that the passage may have been improperly excluded from some manuscripts in order to avoid the impression that Christ had sanctioned adultery: "Certain persons of little faith, or rather enemies of the true faith, fearing, I suppose, lest their wives should be given impunity in sinning, removed from their manuscripts the Lord's act of forgiveness toward the adulteress, as if he who had said, Sin no more, had granted permission to sin."
As for the different accounts in Matthew, Mark, Luke and John it's not that they are different in facts, but rather in details that one noticed over the other. This is 4 different vantage points, even in the the earliest canonical writings they do not differ in validity but just in the 4 different ways of noticing details. You will find that John (the beloved) and Luke (doctor) were far more detailed than Matthew or Mark.