How does the angel Gabriel identify himself
Like this:
Luke 1:19
The angel answered, "I am
Gabriel. I stand in the presence of God, and I have been sent to speak to you and to tell you this good news.
and how come you all don't worship the same God, it seems to be the same God as Jews and Christian so what makes Allah different?
Allah claims he has no son in any sense of the word. YHWH claims He does.
YHWH:
6 I will say to the north, Give them up! And to the south, Do not keep them back!
Bring My sons from afar, And My daughters from the ends of the earth 7 Everyone who is called by My name, Whom I have created for My glory; I have formed him, yes, I have made him. Isaiah 43:6-7
Psalms 2:7, I will declare the decree: The LORD has said to Me, You are My Son,
Today I have begotten You. (Greek translation)
Psalms 2:7, "Let me tell of the decree: the LORD said to me,
'You are My Son,' I have fathered you this day."(Hebrew translation from the Tanakh)
Job 38:4 "Where were you when I laid the foundations of the earth? Tell Me, if you have understanding. 5 Who determined its measurements? Surely you know! Or who stretched the line upon it? 6 To what were its foundations fastened? Or who laid its cornerstone, 7 when the morning stars sang together,
and all the sons of God [beney 'elohim] shouted for joy? (NKJV)
Allah:
The Jews call 'Uzair a son of Allah, and the Christians call Christ the son of Allah. That is the saying from their mouth; (In this) they are intimate; what the Unbelievers of the old used to say.
Allah's curse be on them: how they are deluded away from the truth. [Qur'an 9:30]
"They say (the Christians): "
Allah hath begotten a son!" Glory be to Him! He is self-sufficient! His are all things in heaven and on earth! No warrant have ye for this!" (Surah 10:68)
And they say: "
(God) Most Gracious has begotten offspring." Glory to Him! They are (but) servants raised to honour. Surah 21.26
They say: "
Allah hath begotten a son" :Glory be to Him.-Nay, to Him belongs all that is in the heavens and on earth: everything renders worship to Him. To Him is due the primal origin of the heavens and the earth: When He decreeth a matter, He saith to it: "Be," and it is. Surah 2:116-117
So who was that being? Assuming these events even occurred.
No one knows who that being was. Muhammad's wife's cousin first suggested it was Gabriel and the rest is history.