Is what happened, regarding the disfigurement of the young man's corpse three hours after his burial—which was said to be a result of the torment of the grave—in accordance with Islamic law?

The torment of the grave is a truth established by religious texts, and there is no impediment to Allah making some people aware of the effect of the torment suffered by those who are being punished. As for the story mentioned, there is nothing to prove its authenticity, but there is no religious impediment to its occurrence.