If I want to learn about Mohammed I will go to the source (Koran). If I want to learn about Jesus I will go to the source (New Testament). If I want to learn about Moses, Abraham, Noah I will go to the source (Dead Sea Scrolls), the oldest of theses belong to Enoch, in the Book Of Enoch these people are found, the One who writes the story first is the Author of that story, Enoch is the Author this story.
If GOD allowed this change to occur, it is because GOD disapproved of this book called the Bible, there are no contradictions in the Book Of GOD (Enoch), no lies, no inconsistencies.
Yeah of course, because if you go back to the source you would realize which one should be accepted as 100% god words and which shouldn't. Since the Bible have many contradictions we can never consider it as 100% god's book because God can never contradict himself, however in the Bible there are countless contradictions so we know that it's not God's word, while it main contain some of God Words but maybe humans changed it or remove...etc
Same thing goes for the Old Testament because there are contradictions. Same thing goes for the Hindu scriptures, but when you go to the Islamic source which is the Quran there is no single contradiction, not even 1 for 14 century no humans could come up with a single contradiction in the Quran, the only reason for that because the Quran as promised by God himself it's his responsibility to make it safe from changing unlike Turah or Enjeel which was the responsibility of the people. Since Quran is considered the last message to humans it's God's responsibility to secure it.
We Muslims believe that Allah sent to all people a messenger to guide them, and gave them books but all of these books has been changed or removed or lost...etc so there was a need for a final book that will remain till the day of judgment unchanged, that's Quran.
Angels are not son of gods but his servants if they were his sons then this god doesn't deserve to be called the "Almighty God" because considering a god is an "Un-Godly" acts and we all know that "Almighty God" means someone who doesn't do un-godly thing and there is nothing like him, if he has sons it means he is like his creations >>> which means he is not God

the moment you can compare or put similarity between God and his creations he shouldn't be considered Almighty God.
Now why we believe Also that Prophet Mohammed is the last messenger of the same god of Moses, Abraham, Noah, Jesus and all the universe, it's because all the old books like Turah, Enjeel...etc have prophecies that Prophet Mohammad will come as the final messenger.
MUHAMMAD (PBUH) PROPHESISED IN THE BOOK OF DEUTERONOMY:
Almighty God speaks to Moses in Book of Deuteronomy chapter 18 verse 18:
"I will raise them up a Prophet from among their brethren, like unto thee, and I will put my words in his mouth; and he shall speak unto them all that I shall command him."
The Christians say that this prophecy refers to Jesus (pbuh) because Jesus (pbuh) was like Moses (pbuh). Moses (pbuh) was a Jew, as well as Jesus (pbuh) was a Jew. Moses (pbuh) was a Prophet and Jesus (pbuh) was also a Prophet.
If these two are the only criteria for this prophecy to be fulfilled, then all the Prophets of the Bible who came after Moses (pbuh) such as Solomon, Isaiah, Ezekiel, Daniel, Hosea, Joel, Malachi, John the Baptist, etc. (pbut) will fulfill this prophecy since all were Jews as well as prophets.
However, it is Prophet Muhammad (pbuh) who is like Moses (pbuh):
i) Both had a father and a mother, while Jesus (pbuh) was born miraculously without any male intervention.
[Mathew 1:18 and Luke 1:35 and also Al-Qur'an 3:42-47]
ii) Both were married and had children. Jesus (pbuh) according to the Bible did not marry nor had children.
iii) Both died natural deaths. Jesus (pbuh) has been raised up alive. (4:157-158)
Muhammad (pbuh) is from among the brethren of Moses (pbuh). Arabs are brethren of Jews. Abraham (pbuh) had two sons: Ishmail and Isaac (pbut). The Arabs are the descendants of Ishmail (pbuh) and the Jews are the descendants of Isaac (pbuh).
Words in the mouth:
Prophet Muhammad (pbuh) was unlettered and whatever revelations he received from Almighty God he repeated them verbatim.
"I will raise them up a Prophet from among their brethren, like unto thee, and will put my words in his mouth; and he shall speak unto them all that I shall command him."
[Deuteronomy 18:18]
iv) Both besides being Prophets were also kings i.e. they could inflict capital punishment. Jesus (pbuh) said,"My kingdom is not of this world." (John 18:36).
v) Both were accepted as Prophets by their people in their lifetime but Jesus (pbuh) was rejected by his people. John chapter 1 verse 11 states, "He came unto his own, but his own received him not."
iv) Both brought new laws and new regulations for their people. Jesus (pbuh) according to the Bible did not bring any new laws. (Mathew 5:17-18).
It is Mentioned in the book of Deuteronomy chapter 18:19
"And it shall come to pass, that whosoever will not harken unto my words which he shall speak in my name, I will require it of him."
Muhammad (pbuh) is prophesised in the book of Isaiah:
It is mentioned in the book of Isaiah chapter 29 verse 12:
"And the book is delivered to him that is not learned, saying, Read this, I pray thee: and he saith, I am not learned."
When Archangel Gabrail commanded Muhammad (pbuh) by saying Iqra - "Read", he replied, "I am not learned".
prophet Muhammad (pbuh) mentioned by name in the old testament:
Prophet Muhammad (pbuh) is mentioned by name in the Song of Solomon chapter 5 verse 16:
"Hikko Mamittakim we kullo Muhammadim Zehdoodeh wa Zehraee Bayna Jerusalem."
"His mouth is most sweet: yea, he is altogether lovely. This is my beloved, and this is my friend, O daughters of Jerusalem."
In the Hebrew language im is added for respect. Similarely im is added after the name of Prophet Muhammad (pbuh) to make it Muhammadim. In English translation they have even translated the name of Prophet Muhammad (pbuh) as "altogether lovely", but in the Old Testament in Hebrew, the name of Prophet Muhammad (pbuh) is yet present.
Prophet Muhammad (pbuh) in the New Testament:
Al-Qur'an Chapter 61 Verse 6:
"And remember, Jesus, the son of Mary, said, 'O Children of Israel! I am the messenger of Allah (sent) to you, confirming the Law (which came) before me and giving glad tidings of a messenger to come after me, whose name shall be Ahmed.' But when he came to them with clear signs, they said, 'This is evident sorcery!' "
All the prophecies mentioned in the Old Testament regarding Muhammad (pbuh) besides applying to the Jews also hold good for the Christians.
1.John chapter 14 verse 16:
"And I will pray the Father, and he shall give you another Comforter, that he may abide with you forever."
2.Gospel of John chapter 15 verse 26:
"But when the Comforter is come, whom I will send unto you from the Father, even the Spirit of truth, which proceedeth from the Father, he shall testify of me."
3. Gospel of John chapter 16 verse 7:
"Nevertheless I tell you the truth; it is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you".
"Ahmed" or "Muhammad" meaning "the one who praises" or "the praised one" is almost the translation of the Greek word Periclytos. In the Gospel of John 14:16, 15:26, and 16:7. The word 'Comforter' is used in the English translation for the Greek word Paracletos which means advocate or a kind friend rather than a comforter. Paracletos is the warped reading for Periclytos. Jesus (pbuh) actually prophesised Ahmed by name. Even the Greek word Paraclete refers to the Prophet (pbuh) who is a mercy for all creatures.
Some Christians say that the Comforter mentioned in these prophecies refers to the Holy Sprit. They fail to realise that the prophecy clearly says that only if Jesus (pbuh) departs will the Comforter come. The Bible states that the Holy Spirit was already present on earth before and during the time of Jesus (pbuh), in the womb of Elizabeth, and again when Jesus (pbuh) was being baptised, etc. Hence this prophecy refers to none other than Prophet Muhammad (pbuh).
Gospel of John chapter 16 verse 12-14:
"I have yet many things to say unto you, but ye cannot bear them now. Howbeit when he, the Spirit of truth is come, he will guide you unto all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come. He shall glorify me".
The Sprit of Truth, spoken about in this prophecy referes to none other than Prophet Muhammad (pbuh)
Muhammad (pbuh) prophesised in the Rigveda
A prophecy is also found in Rigveda Book I, Hymn 53 verse 9:
The Sanskrit word used is Sushrama, which means praiseworthy or well praised which in Arabic means Muhammad (pbuh).
uhummad (pbuh) is also prophesised in the Samveda
Prophet Muhammad (pbuh) is also prophesised in the Samveda Book II Hymn 6 verse 8:
"Ahmed acquired from his Lord the knowledge of eternal law. I received light from him just as from the sun." The Prophecy confirms:
1. The name of the Prophet as Ahmed since Ahmed is an Arabic name. Many translators misunderstood it to be Ahm at hi and translated the mantra as "I alone have acquired the real wisdom of my father".
2.Prophet was given eternal law, i.e. the Shariah.
3.The Rishi was enlightened by the Shariah of Prophet Muhammad. The Qur’an says in Surah Saba chapter 34 verse 28
"We have not sent thee but as a universal (Messenger) to men, giving them glad tidings and warning them (against sin), but most men understand not." [Al-Qur'an 34:28]
And finally The Quran Challenge 
And if you are in doubt as to what WE have sent down to OUR servant (Mohammed), then produce a chapter like it, and call upon your helpers besides ALLAH, if you are truthful. But if you do it not - and never shall you do it - then guard against the Fire, whose fuel is men and stones, which is prepared for the disbelievers.