How can a man know that the god he believes in and worships is the true God?

when you die you find out. so you can get back to us

But of all these gods there must be only one true God and all the others are false gods.

Why do you believe this? Why must there only be "one true god"?

Because of the voice in his head which he calls the Spirit of Ama.

He knows everything, including what happened in the past and what will happen in the future.

But if that is true, why would it not have aborted its creation project after seeing the future and knowing that humans would cause it to become angered? Didn't the god know that its penchant for justice would consume even its mercy?

God knows that what He created was wicked and evil continually

He will settle accounts with each one of us, which we call Judgment Day.

One of the criteria that could be employed to find the True God is, what is his record of reliability? Is he able to foretell events far into the future and then that prophecy come true in every detail? Note an example.

One of the most remarkable prophecies regarding the downfall of the ancient world power, Babylon, involved its conqueror, King Cyrus of Persia. Nearly two centuries before Cyrus rose to power, Jehovah God mentioned him by name and foretold that he would be the one to conquer Babylon.

Pointing forward to Cyrus’ conquest, Isaiah was inspired to write: “This is what Jehovah has said to his anointed one, to Cyrus, whose right hand I have taken hold of, to subdue before him nations, . . . to open before him the two-leaved doors, so that even the gates will not be shut.” God also foretold that the Euphrates River would, in effect, dry up.—Isaiah 45:1-3; Jeremiah 50:38.

Greek historians Herodotus and Xenophon confirm the fulfillment of this amazing prophecy. They reveal that Cyrus diverted the Euphrates River, causing its waters to recede. Cyrus’ armies thus gained access to the city through its gates, which had been left open. As foretold, mighty Babylon fell “suddenly,” in one night.—Jeremiah 51:8.

To me, the prophecies of the true God is 100% reliable. I am not including others because they may be different from my perception.

For example, the true God said to Isaiah that God would become a man. He wrote in Isaiah 9:6, "For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counselor, The mighty God, The everlasting Father, The Prince of Peace." Isaiah lived about 700 years before Jesus.

World War III will start at Spratly Islands in the middle of the year on a Wednesday. This has not happened yet but I guess it would happen next year, on 2018-07-03, because Jesus would have been 32 solar years old, there is tension between North Korea and the US, there is tension between China and the US over Spratly Islands, the platform of the spirit of Ama died this year. I first heard this prophecy on 1986-06-13, and developed over the years.

izzythepush cited that two European nations have more than one President, so I'll use Prime Minister. There is one Prime Minister like there is one true God. The others are false gods.