I provided the verses which show you in error. Read them, in context:
Did you read them?
As for Isaiah 65:20, it is not referring to physical death. It is referring to maturity, of childhood passing to adult hood, at 100 years, rather than what we currently experience of around 18-21, and as for the sinner, they are still yet dead and accursed in the second death, not actually living (gone for ever), even after 100 years later. Consider:
Isa 65:20 There shall be no more thence an infant of days, nor an old man that hath not filled his days: for the child shall die an hundred years old; but the sinner being an hundred years old shall be accursed.
[Context: Isaiah 65:17 KJB - For, behold, I create new heavens and a new earth: and the former shall not be remembered, nor come into mind.]
Shall we not see how the text begins with:
"There shall be no more thence an infant of days", in comparison to the latter part of the text?,
"the child shall die an hundred years old". These two together speak of a childhood that lasts 100 years, before becoming an adult.
The Bible [KJB] in several places speaks of
"the days of thy youth",
"days of his youth",
"yet a youth",
"but a youth" which ceases at manhood, for the
"days of youth [as a child]" are not endless, but have a set time, for a period of growth [thus as Ecclesiastes says, a
"time to die" [Ecclesiastes 3:2 KJB]], for instance:
Psalms 144:12 KJB - That our sons may be as plants grown up in their youth; that our daughters may be as corner stones, polished after the similitude of a palace:
In further context, we read:
Isaiah 65:22 KJB - They shall not build, and another inhabit; they shall not plant, and another eat: for as the days of a tree are the days of my people, and mine elect shall long enjoy the work of their hands.
The children in the New Heavens and New Earth do not stay youth forever, but grow up, and thus the youth dies, is
"passed away", ceases to be youth, and is now adult, thus the phrase of 'passing' into adulthood:
Malachi 4:2 KJB - But unto you that fear my name shall the Sun of righteousness arise with healing in his wings; and ye shall go forth, and grow up as calves of the stall.
Paul says something similar:
1 Corinthians 13:11 KJB - When I was a child, I spake as a child, I understood as a child, I thought as a child: but when I became a man, I put away childish things.
Ephesians 4:15 KJB - But speaking the truth in love, may grow up into him in all things, which is the head, even Christ:
As for the accursed sinner, they are still dead (2nd death) then, for the contempt is upon them, not by them:
Dan 12:2 And many of them that sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt.
We do this still to this day, with people like Hitler, Pol Pot, Stalin, etc, who when their names are mentioned, or thought upon, are derided, known as evil wicked persons, infamous, yet not actually living, though they have been dead some time. It will be written against them in God's book forever.
We can look at any text you like. I will show you by God's grace.