For now, we will just discuss only three religions, Christianity, Judaism and Islam. We are going to start with the most common religion(The one with the most number of believers but unfortunately lesser no. of in depth followers), Christianity.
Note: We have omitted the possibilities of alternation of the Holy scripture(In Christianity Bible or In Judaism Tanakh or the Hebrew Bible).

Concept of God in Christianiaty(Christian definition of God)?

About God in Christianity, a famous theologist James A. Flower said,

"What God is, only God is. God does what He does, because He is who He is."

In Christianity, one may get confused in the son and the father concept, but they believe both are the same, they are not seperate.

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God revealed Himself supernaturally in the incarnation of His Son, Jesus Christ.
-(cf. John 1:14; 14:9).

The question which arises in every healthy mind is, can God be limited in time(by time I mean the incarnation of Jesus into a human body)? or Can a limited be called God? For further explanation checkout the last post.

In Christianity God is one, then can two be called one? or If they are one, Aren't they parted away(Can God have two or multiple parts?)?
This post is just to get more direct knowledge from fellows here, answers will be much appreciated!

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Concept of God In Judaism(Jewish definition of God)?

The fact of God's existence is accepted almost without question. Proof is not needed, and is rarely offered. The Torah(The Holy scripture in Judaism) begins by stating "In the beginning, God created..." It does not tell who God is or how He was created. Judaism does not seek out converts and the one who converts will still be A Jew and actively discourages in converts.

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Concept of God In Islam(Islamic definition of ALLAH)?

Concept of God in Islam is not limited by any mean, He is the creator, the perfect, the greatest of all, the supreme and the most knowledge able(not bound in time domain and not limited) and in Islam God have 99 attributes(all mentioned in the Holy Quran-which is the only scripture without any alternation). But the word "ALLAH" is the most precise and the most commonly used word for God in Islam. Islamic definition of God is rather more precise as 99 of His attributes(revealed) clarifies all the doubts. Moreover when we see monotheism, by definition the concept of God in Islam best fits in.