. The Devil is, after all, a former angel, a creation of God. .

Note that the highest angel was equal to the Archangel Michael. Lucifer was the best angel (if I'm not mistaken), but he wanted to become a god himself and persuaded the angels who were subordinate to him to do the same. These angels later became devils, demons, and so on.

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And he is fulfilling the function given to him by God. .

He was fulfilling it, before his fall.

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But he is not tempting people to distract them from God. .

No, he is tempting them. He harbors hatred towards the human race, which was created in the image of God, and he tempts people so that they will suffer as he does.

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The Devil also has it hard, because he is blamed for everything. .

Because he is largely to blame.

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God will never punish him, because he loves the Devil too.

This is already a distortion of Christianity; heretics were burned at the stake for this. God does not punish him so that there would be a test for human souls.