Your key question is: Are there several universes?
Your secondary questions (indicated through your clarification) are:
Where is Allaah?
What are the heavens that Allaah has mentioned in the Qur'aan?
Is it safe to say we can never fully understand Allaah?
What are the capabilities of Allaah?
Is knowledge only what is in the Qur'aan?
Are there intelligent beings (life) apart from us?
So you have put in a lot of questions without explicitly mentioning them and let me try to help you understand them, insha Allaah.
Are there several universes?
First, it depends on what you understand by the term universe.
Definition:
Universe is everything that exists, including stars, planets, earth,
space and so on. (from Oxford dictionary).
But I think what you mean to ask is "are there any other planets like earth in which people live?". Whether one can or can't live in them is a different matter. But do they exist?
Answer: Yes, there are many earths. Allaah has mentioned in the Qur'aan:
اللَّـهُ الَّذِي خَلَقَ سَبْعَ سَمَاوَاتٍ وَمِنَ الْأَرْضِ
مِثْلَهُنَّ
(From: Surah At-Talaaq)
Meaning:
It is Allaah who has created seven heavens and of the earth, the like
of them.
So He has created 7 earths like He has created 7 heavens.
There is a lot of information from the Qur'aan and the hadeeth that explain that for example, the distance between each sky (heaven) and each earth is 500 years.
Source of the above (online): http://www.answering-islam.org/Quran/Science/seven_earths.html
Where is Allaah?
Clearly, without any doubt, Allaah is above everything. This is our belief as Muslims. We don't believe that Allaah lives in the earth like us, for we are His creation and He is the Creator. The Creator does not mix in the creation.
Source:
الرَّحْمَـٰنُ عَلَى الْعَرْشِ اسْتَوَىٰ
(From: Surah Taaha)
Meaning: The most merciful (who is) established above the throne
This is only one example but if you take the time, you'll find many, insha Allah.
What are the heavens that Allaah has mentioned in the Qur'aan?
We often see translations to use the word heaven or heavens. I believe it must be clear from the previous (first answer) that the term is used to refer to skies.
In Arabic, Sky is سماء (samaa) and Skies is سماوات (samaawaat).
Is it safe to say we can never fully understand Allaah?
No, do not say that. We know of Allaah what He has revealed to us through the Qur'aan and what has been taught to us by the noble prophet Muhammad (sal). We do not attribute to Him other than this. We do not reject any of what has been told in there. What is unknown to us remain unknown but HE is the knower of everything, including what is hidden in our hearts.
What are the capabilities of Allaah?
We learn from the Qur'aan, what Allaah has said about himself:
وهو على كل شيء قدير
Meaning: He has power over everything.
What HE will or is capable of doing, He has mentioned to us through the Qur'aan and the hadeeth. Other than that, we do not know. You and I, we don't even know what we will be able to do in another 10 years, if we live that long. So if it's not in the sources mentioned, don't bother tiring yourself trying to think of what Allaah can do. Islam is revelation and not logical reasoning. So we take what's in the revelation, for our little minds cannot comprehend the greatness of our Creator's capabilities, except what has been told to us.
Is knowledge only what is in the Qur'aan?
No. Knowledge of Islam is revealed in the Qur'aan. Then our loving teacher, the messenger Muhammad (Sal) taught and explained it to us. Actually to his companions. And they were the best of students to practise it. Allaah has mentioned this in the Qur'aan referring to them:
رضي الله عنهم ورضوا عنه
Meaning: Allaah is pleased with them and they are pleased with Him.
So these narrations are preseved as Hadeeth. The saheeh of Bukhaari and Muslim are some examples. So the Qur'aan and the authentic ahaadeeth are both our sources.
Are there intelligent beings (life) apart from us?
If you go through the Tafseer of ibn Katheer, you should find that the earth was inhabited before us by the Jinns (Jaan) - i.e., demons. So when the Allaah mentioned to the Angels that He was going to create mankind, the angels asked Him if He was going to do something that would cause bloodshed. You find this in the opening verses of Surah Al-Baqarah.
So we learn that Allaah has mentioned the Angels, Jinn, Makind, then animals and insects.
Personally I don't know of any reference to aliens, if that's what you're talking about. And personally I don't believe all those stories about aliens from Mars or anywhere else as promoted by modern scientists.
The earth is big enough and we haven't yet learnt about it or discovered it. Aliens? No, not in my records and Allaah knows best.
