The matter of interpolations is far more difficult to discern though there are instances where modern scientific methods have been able to find erasures and interpolations in ancient manuscripts.
Now changes from the oldest manuscripts that are known today just require a bit of comparison.
The two oldest 'complete' New Testaments are found in the Codices Vaticanus and Sinaiticus, both of which are dated to the first half of the 4th century CE. The Codex Alexandrinus is believed to have been written during the 5th century. All three have multiple differences from the text most Christians know today.
"In any event, none of [the original manuscripts of the books of the Bible] now survive. What do survive are copies made over the course of centuries, or more accurately, copies of the copies of the copies, some 5,366 of them in the Greek language alone, that date from the second century down to the sixteenth. Strikingly, with the exception of the smallest fragments, no two of these copies are exactly alike in their particulars. No one knows how many differences, or variant readings, occur among the surviving witnesses, but they must number in the hundreds of thousands."
The Orthodox Corruption of Scripture, Bart Ehrman, pp. 27
Examples:
Codex Vaticanus: Verses not found in this codex that are present in the KJV
Matthew 12:47;16:2b-3;*17:21;*18:11;*23:14;
Mark 7:16; 9:44.46;*11:26;*15:28
Luke 17:36,22:43–44
John 5:4,Pericope Adulterae (John 7:53–8:11);
Acts 8:37; 15:34, 24:7; 28:29;
Romans 16:24.
1 Peter 5:3.
This info found in the following book
Metzger, Bruce M.*(2001).*A Textual Commentary on the Greek New Testament.
Codex Sinaiticus
Mark 16 which tells of the three women, Mary Magdalene, Mary – mother of James and Salome going to the tomb to anoint Jesus body. Codex Sinaiticus ends the chapter at verse 8
“Trembling and bewildered, the women went out and fled from the tomb. They said nothing to anyone, because they were afraid.” Modern Bibles continue the tale with verses 9 to 20
The Lord’s Prayer (Matthew 6:9–13)
Father, Hallowed be thy name,
Thy kingdom come. Thy will be done, as in heaven, so upon earth.
Give us day by day our daily bread
And forgive us our sins, as we ourselves also forgive every one that is indebted to us.
And bring us not into temptation.
John 8: 3–11 is not found in the codex, nor are the verses Luke 9:55–56
Luke 24:51 does not have the phrase “and was taken up into heaven”
These and other verses missing from the oldest texts were evidently viewed by the interpolators and editors as providing some justification for the beliefs of the Gnostics, Docetics, Arians and Adoptionists.