Supreme God in Islam
Quran Sharif (قرآن شریف) or Quran Majid is the most revered religious text in Islam. The Quran was revealed on Prophet Muhammad via Jibril (an angel) over a period of 23 years. It is considered to be the "Word of God". Angel Jibril revealed this to Prophet Muhammad without any distortion or omission.
The instructions in Quran are considered to be the instructions from God.
The God of Quran talks about some other Supreme God
Muslims consider the God who gave the knowledge of Quran to be the Supreme God where as the God in Quran indicates towards some other God who is Supreme.
In Surah Furqan 25: 52 - 59 the God of Quran talks about some other Supreme God.
Surat Al Furqan 25: 52 - 59
25:52 - So do not obey the disbelievers, and strive against them with the Qur'an a great striving.
25:53 - And it is He who has released [simultaneously] the two seas, one fresh and sweet and one salty and bitter, and He placed between them a barrier and prohibiting partition.
25:54 - And it is He who has created from water a human being and made him [a relative by] lineage and marriage. And ever is your Lord competent [concerning creation].
25:55 - But they worship rather than Allah that which does not benefit them or harm them, and the disbeliever is ever, against his Lord, an assistant [to Satan].
25:56 - And We have not sent you, [O Muhammad], except as a bringer of good tidings and a warner.
25:57 - Say, "I do not ask of you for it any payment - only that whoever wills might take to his Lord a way."
25:58 - And rely upon the Ever-Living who does not die, and exalt [ Allah ] with His praise. And sufficient is He to be, with the sins of His servants, Acquainted -
25:59 - He who created the heavens and the earth and what is between them in six days and then established Himself above the Throne - the Most Merciful, so ask about Him one well informed.
In the lines above the God of Quran is clearly speaking about some other Supreme God who created everything in 6 days and then sat on a throne.
This proves that the Supreme God is different to the God of Quran and moreover He is not formless as He sat on a throne. This also proves that the God is in form.
Qualities of Supreme God - Surat Al Ikhlaas 112: 1 - 4
112:1 - Say, "He is Allah , [who is] One,
112:2 - Allah , the Eternal Refuge.
112:3 - He neither begets nor is born,
112:4 - Nor is there to Him any equivalent."
The above 4 qualities are as it is applicable to God Kabir (Allah Kabir) who is eternal, is never born and there is no one equivalent to God Kabir.