Sure I’ll jump on this.
Lucifer or “Light-bearer” is the name of the leader of the angels who rebeled against God. (I mention this so that the meaning of the quoted scriptural passage can be seen to clearly apply to Lucifer/Satan/The Devil.)
After being tempted by a devil during his 40 days of fast, Christ commands “Depart from me ye cursed into everlasting fire which was prepared for the devil and his angels.” Matt XXV, v41.
Now the “everlasting fire” reffered to is of course Hell. And the adjective “everlasting” used here clearly indicates the duration of their stay there. Therefore, noone who goes to Hell has any hope of salvation from there.
Now angels are purely spiritual beings. They have not the impediments to intellect that man has, thus there guilt is immeasurably greater than mans. Therefore God showed mercy to men when they sinned, though he spared not the angels when they sinned:
Gen II “THey rebelled against God - Lucifer, their leader, saying: “We shall be like unto the Most High; we will place our throne above the stars.” Then there was a great strife in heaven. Micheal and the otherangels who remained faithful to God, fought against the bad and rebellious spirits, whose chief is now called Satan, or the devil. The bad angels were conquered, and cast from heaven down to hell.”
Christ came specifically to redeem man, not the angels, who had no need, nor devils (fallen angels) who had already been judged and condemned to hell, but only for man. “For God so loved the world, that He sent His only Son . . .” Man needed redemption. God became man to redeem Man, not to redeem spiritual beings. Jesus died on the cross that Man might live, not that devils would be restored to life.
Finally, it would be pointless to pray for one in Hell, and since we know Satan is in Hell, we know we cannot help him by our prayers. But our prayers for someone who is deceased will be applied by God in a manner befitting the prayers. Thus you may pray for any deceased human, and though they might be in Hell, your prayers will not be wasted.
JPL