Isaiah 56:1 Thus saith the LORD, Keep ye judgment, and do justice: for my salvation is near to come, and my righteousness to be revealed. (No one on earth knows God's righteousness. It is the key of God's judgment in the last day.)

God wants people to have righteous knowledge to be fine human being and secure their soul in a good place. People need to learn God's righteousness, and only the true Messiah / Christ who exists at present time, he can tell people about God's righteousness, and this will be the final fact-of-life of mankind.

Human need good knowledge (experiences) to be on earth, and need right spiritual knowledge to continue their good conducts as a human being and continue secure their soul after their dead.

Fact of Human Life:
A normal person must have two main parts combined to be one human being. First the body, and second the soul. Without one of them, there will not be a completed human being..

Life and body:
Life is a combination of the body and soul, but the body contains functional substances that allows it to function without the soul. If anyone is interested in this subject, he/she can study the scientific research about "Out of Body Experience" (OBE) by the meditation, and "Near Death Experience (NDE)"

Being "Dead" means the body cannot function and it is without the soul.

Life and soul:
Life is life and soul is soul. They are completely separated. Here is a simple comparison:
The Body is like a car, and the soul is the driver of that car. The car can run without the driver, but the car has no control without the driver (We are not using any of the artificial intelligence that can be used to control and navigate a vehicle by attaching sophisticated equipment to it ).

The Soul that is without a body cannot perform normal human activity. In some cases though, the soul may be able to communicate with a living person, but it is not completely by control.

What did Rev 20:4 "...the souls of them that were beheaded for the witness of Jesus" means?

It means that people who trust Jesus, their soul have no head. These people do not have word of God which are wisdom and understanding, but they have faith. Their destination is the lake of fire. Only the true Christ could help them out from the trouble.

God is verifiable real:
It is possible to verify that God is real by using scientific fact. And only the true Messiah will be able to perform this testimony.

Hell and Heaven are fact:
The true Messiah is able to verify that hell and heaven are real by revealing the facts. But people must first verify the truth of the true Messiah.

No Dead:
It would be simple to say the Dead are in hell, and the living are in the heaven.