Mr. Lennon knows NOW that there’s a Hell. And he can probably surmise that somewhere far away from where he is eternally incarcerated, there’s also a Heaven.
John 3:18 “He that believeth shall not be condemned, but he that believest not is condemned already, because he hath not believed on the name of the only begotten Son of God.”. Only a fool would sing “IMAGINE”.
That’s too bad.
Every week, as we Orthodox Christians prepare to receive Holy Communion, we pray a series of preyers in preparation for receiving the Holy Mystery. One of them is this:
https://www.orthodoxsalem.com/communion-prayers-st-basil-the-great
As it states in the prayer:
....For Thou dost not wish, O Master, that the work of Thy hands should perish, neither dost Thou take pleasure in the destruction of men, but Thou desirest that all men should be saved and come to the knowledge of the truth.....
This is entirely Scriptural:
https://biblehub.com/1_timothy/2-4.htm
Nevertheless, singing—or creating—such packs of lies as “Imagine” does not further one’s salvation!