In the Book of Revelation we have teachings Jesus gave after losing mortality. He died and rose. He died mortal and rose immortal. Yet it is not a case that his teachings as one made immortal by God are superior and override his teachings given in his mortality. The teachings in the gospels are needed too. He was giving them as a mortal subject to mortal life issues like we are. We need those gospel teachings too, and must not replace them with the teachings in the Book of Revelation. When he was previously a mortal facing death, he proclaimed that if you do not believe he is the one he has been saying he is, in other words that he the light of the world sent by the Father, you will die in your sins. In other words: If you do not believe he is the light, you would not give sufficient weight to his teachings to learn and live by them permanently, and then know the truth from him that sets you free from the trappings of sin. These teachings he referred to, are the gospel teachings given in his days of mortal flesh. The Book of Revelation is important too, especially when by baptism we are united with him in his immortal eternal state. But they supplement those given previously in his mortal weakness.
