On everlasting life.
Well, we already know that Adam and Eve had life everlasting if they obeyed Almighty God, but they sinned before God and eventually died, as they were banned from the tree of life. So everlasting life does not equal or mean immortality as we know an immortal being cannot die.
How do we know this? Almighty God is immortal and owns immortality, and he cannot die.
1Tim 6:16: who only hath immortality, dwelling in light unapproachable; whom no man hath seen, nor can see, to whom be honor and power eternal. Amen. – KJV
On the other hand, being immortal does equal living forever. Those who inherit everlasting life are those who believe in Christ Jesus as it stated many times in the scriptures John 3:15: “that whoever believes in him may have eternal life.”
On messengers or angels and everlasting life.
Also, on the thought of everlasting life of another kind, when answering a trick question from the Sadducees about whose wife would a woman be in the resurrection after having married seven men Jesus said this:
Luke 20:34-36 And Jesus said to them, “The sons of this age marry and are given in marriage, but those who are considered worthy to attain to that age and to the resurrection from the dead neither marry nor are given in marriage, for they cannot die anymore, because they are equal to angels and are sons of God, being sons of the resurrection.
It therefore also seems Gods messengers are noted as living forever likely due to their nature of being spirits, but they are not immortal as we know only God is immortal and now Christ.
On immortality (Athanasian - ΑΘΑΝΑΣΙΑΝ).
Only mentioned 3 times in the Bible what is immortality?
We know that Almighty God is immortal and is not dependent on anyone else for life. But he is also the source of life.
Jesus was also given immortality upon his resurrection.
John 5:26 For even as the Father has life in Himself, thus to the Son also He gives to have life in Himself. - CLV
So, from John, we can see immortality is having "life within oneself".
God has though, through his grace, bestowed immortality and incorruption upon those whom He has chosen and sealed as a new creation. This would also mean that such individuals could exist apart from their Almighty Father if need be.
John 5:26 For as the Father has life in himself, so he has granted the Son also to have life in himself.
2Cor 5:17 Therefore, if anyone is in Christ, he is a new creation. The old has passed away; behold, the new has come.
Gal 6:15 For neither circumcision counts for anything, nor uncircumcision, but a new creation.
1Cor 15:53-54 For this corruptible must put on incorruption, and this mortal must put on immortality. So when this corruptible shall have put on incorruption, and this mortal shall have put on immortality, then shall be brought to pass the saying that is written, Death is swallowed up in victory. – KJV
On incorruption/incorruptibility (ΑΦΘΑΡΣΙΑΝ/ΑΦΘΑΡΤΟΥ – Aphtharsian or Aphthartou)
Only Yahweh the Almighty God and Christ Jesus are known to be incorruptible, unable to be turned to darkness or sin. But soon as part of their reward the chosen holy ones will also receive incorruptibility too.
Rom 1:23 And changed the glory of the incorruptible God into an image made like to corruptible man, and to birds, and four-footed beasts, and creeping things. – AKJV
Yes, incorruptibility is yet another gift that goes along with immortality, that is bestowed onto those who are called and conquer, faithful till death or their ascendance.
Rom 2:7 to them that by patience in well-doing seek for glory and honor and incorruption, eternal life – ASV
1Cor 15:42 So also is the resurrection of the dead. It is sown in corruption; it is raised in incorruption
1Cor 15:53-54 For this corruptible must put on incorruption, and this mortal must put on immortality. So when this corruptible shall have put on incorruption, and this mortal shall have put on immortality, then shall be brought to pass the saying that is written, Death is swallowed up in victory. – KJV
2Tim 1:10 but hath now been manifested by the appearing of our Savior Christ Jesus, who abolished death, and brought life and incorruption to light through the gospel - ERV
1Pet 1:23 Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth for ever. - KJV
Therefore, while incorruption is often associated with immortality, incorruption is not immortality as can be seen from 1Cor 15:53-54 quoted above.
Incorruption is the inability to be corrupted, sin or be disobedient. No wonder this gift of being a ‘new creation’ is one superlative in nature and truly extraordinary.
IMHO it seems prudent that an immortal being is also made incorruptible otherwise if it were possible to corrupt such ones it would be very bad indeed. Also note that receiving immortality and thus being able to exist aside from God as the source of life provokes the question, are they meant to do something else after they fulfil their roles?