1a. Does the Koran (not the Hadith’s or the Tafsir) say that the Bible was corrupted?
RKC: The Qur'an makes reference to this is Surah 2. Surah 5:12-15, 3:78, 4:46, 6:91 shed some light on this as well.
Surah 2 79. Then woe to those who write the Book with their own hands, and then say:"This is from Allah," to traffic with it for miserable price!- Woe to them for what their hands do write, and for the gain they make thereby.
1b. If so, before or after the Koran and by whom?
RKC: The above ayat is referring to something that occurred before the Qur'an came, but has the same condemnation for anyone between Muhammad's (P) time and now. Specific verses would have to be examined to explore when the change happened. What's important is that a change happened and the reliability of the given verse MUST be questioned as coming from God.
As to "whom", my answer would be "not God" or "man". Consider the below verses from the book of 1 John. The below verses from the Kings James version of the Bible is probably the most supportive scripture for the Trinity. Yet, a panel of Christians (Catholic & Protestants) and Jews found significant reason to change this passage in the Revised version. I doubt they knew/know who or when the passage was "altered", but felt the need to correct it.
1 John 5:6-9 (Kings James Version) 6 This is he that came by water and blood, even Jesus Christ; not by water only, but by water and blood. And it is the Spirit that beareth witness, because the Spirit is truth. 7 For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one. 8 And there are three that bear witness in earth, the Spirit, and the water, and the blood: and these three agree in one. 9 If we receive the witness of men, the witness of God is greater: for this is the witness of God which he hath testified of his Son.
1 John 5:6-9 (Revised Version) 6 This is he who came by water and blood, Jesus Christ, not with the water only but with the water and the blood. 7 And the Spirit is the witness, because the Spirit is the truth. 8 There are three witnesses, the Spirit, the water, and the blood; and these three agree. 9 If we receive the testimony of men, the testimony of God is greater; for this is the testimony of God that he has borne witness to his Son.
In addition, the Qur'an has given us a criteria to judge if a divine scripture has been tampered with.
Surah 4 82. Do they not consider the Qur'an (with care)? Had it been from other Than Allah, they would surely have found therein Much discrepancy.
Webpages, such as this one, list hundreds of discrepancies in the Bible, but they are relatively minor. I try to look at material doctrinal issues. For instance...after reading John 5:30 and Mark 14:36, we should be asking, "How can a divine being who is One, have two or three separate wills?" or like the below link that discusses the Great Commission. These are the types of scriptural analysis that I find interesting.
2. Does the Koran (not the Hadith’s or the Tafsir) clearly state that it’s message abrogates the messages spoken by all of the prophets that came before Mohammed.
3. If Allah’s words cannot be corrupted, does the Koran make it clear why Allah allowed his message communicated to the prophets that came before Mohammed to be corrupted or hidden?