It seems appropriate to check the source of information on prayer.

Regarding God's omniscience, "And when you pray, do not keep on babbling like pagans, for they think they will be heard because of their many words. Do not be like them, for your Father knows what you need before you ask him."

Why pray? God frequently relents from justice and grants mercy when asked. Both justice and mercy are good; switching 'tween them when asked seems much less capricious than any arbitrary system.
>"Then Abraham approached him and said: "Will you sweep away the righteous with the wicked? What if there are fifty righteous people in the city? Will you really sweep it away and not spare the place for the sake of the fifty righteous people in it? Far be it from you to do such a thing-to kill the righteous with the wicked, treating the righteous and the wicked alike. Far be it from you! Will not the Judge of all the earth do right?"
>The LORD said, "If I find fifty righteous people in the city of Sodom, I will spare the whole place for their sake."
>Then Abraham spoke up again: "Now that I have been so bold as to speak to the Lord, though I am nothing but dust and ashes, what if the number of the righteous is five less than fifty? Will you destroy the whole city because of five people?"
>"If I find forty-five there," he said, "I will not destroy it."
>Once again he spoke to him, "What if only forty are found there?"
>He said, "For the sake of forty, I will not do it."
>Then he said, "May the Lord not be angry, but let me speak. What if only thirty can be found there?"
>He answered, "I will not do it if I find thirty there."
>Abraham said, "Now that I have been so bold as to speak to the Lord, what if only twenty can be found there?"
>He said, "For the sake of twenty, I will not destroy it."
>Then he said, "May the Lord not be angry, but let me speak just once more. What if only ten can be found there?"
>He answered, "For the sake of ten, I will not destroy it."
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>"Go to the great city of Nineveh and preach against it, because its wickedness has come up before me." [A couple chapters later, the people of Nineveh respond...] "...Let everyone call urgently on God. Let them give up their evil ways and their violence. Who knows? God may yet relent and with compassion turn from his fierce anger so that we will not perish."
>When God saw what they did and how they turned from their evil ways, he had compassion and did not bring upon them the destruction he had threatened.

Regarding who prays, there was never any requirement that the one praying be a Jew or Christian or anything.