Would Jesus have played Minecraft then if he could?

Or he finds the net so good that other people can respawn

No, I think Jesus is too holy. And if he did, he would have added a wine bucket and flooded the nether.

On his own server, is not it possible to enable Hardcore mode for all other players except himself? Java edition required.

No.

Even at the time of the Old Testament, for God is always anxious to save as many as possible, not to judge. He hates to kill.