Who is ALLAH ?
"Allah" is the proper name applied to the Supreme Being and its use predates Islam, and is an Aramaic name.  "Allah" has neither a female nor a plural conjugation.  "Allah" as a word has only been used to describe The Unimaginable Supreme Being who exists by Himself- comprising all attributes of perfection.  "Allah" has no other corresponding translated word in English or any other language.  "Allah" is the name of the God of Noah, Abraham, Moses, Jesus, and Muhammad.  "Allah" is the name of God used by Christians and Jews in Arabia both now and predating Islam.

What does/did ALLAH do? Based on what is written in the Qur'an.

He is the Creator: 
Chapter 4:1, Chapter  6:1-3, Chapter  7:54, Chapter 42:11

He is the Sustainer:
Chapter 4:79, Chapter 22:66, Chapter 65:3-4

He is the Protector:
Chapter 2:257, Chapter 3:102, Chapter 9:116, Chapter 42:31

He is the Guide to Truth:
Chapter 6:39, Chapter 6:125, Chapter 6:149, Chapter 7:178

He is the Judge:
Chapter 10:30-32

What qualities does Allah have?

He is Just:
Chapter 3:108, Chapter 5:8, Chapter 4:79, Chapter 3:182, Chapter 10:44, Chapter 40:20, Chapter 53:39

He is Mighty:
Chapter 6:91, Chapter23:91-93, Chapter 26:217

He is Powerful:
Chapter 5:76, Chapter 6:60-61, Chapter 6:95-96

He is Forgiving:
Chapter 9:104, Chapter 13:30

He is All-Knowing:
Chapter 27:65-66, Chapter 31:30

He is Unchanging:
Chapter 33:62, Chapter 35:43, Chapter 48:23