Although you specifically ask about the designation ‘First and Last’, there is a clear biblical link to that and the oft-concurrent designation ‘Alpha and Omega’, which is abundantly clear in the book of Revelation, and in JW literature. See https://www.jw.org/en/bible-teachings/questions/alpha-omega/ Who or What Is “the Alpha and the Omega”?
“The Alpha and the Omega” refers to Jehovah God, the Almighty. This
term occurs three times in the Bible.—Revelation 1:8; 21:6; 22:13.
…Why does God call himself “the Alpha and the Omega”? Alpha and omega
are the first and last letters of the alphabet in Greek, the language
used to write the part of the Bible commonly called the New Testament,
which includes the book of Revelation. The respective positions of
these letters in the Greek alphabet are used to illustrate that
Jehovah alone is the beginning and the end. (Revelation 21:6) He was
Almighty God in the infinite past, and he will continue to be Almighty
God forever. He is the only one who is “from everlasting to
everlasting.”—Psalm 90:2. Who is “the first and the last”? The Bible
applies this term both to Jehovah God and to his Son, Jesus, but with
More on that later.
Here is another official JW link, ‘Highlights From the Book of Revelation’, 15 January 2009 Watchtower - https://wol.jw.org/en/wol/d/r1/lp-e/2009046#h=11:0-12:0 However, I used the 1988 JW publication “Insight on the Scriptures” Vol. 1 which states (in agreement) that only Jehovah God has the title ‘Alpha and Omega’ in Rev. 1:8. This is because the verse goes on to say this one is “the Almighty” (page 81). JW teaching is that only Jehovah is the Almighty God, and Jesus is the Mighty God (Isaiah 9:6) This explains two points in their article on ‘Alpha and Omega’:
(1) “Although the preceding verse  speaks of Christ Jesus, it is clear that in verse 8 the application of the title is to ‘the Almighty’ God.” Then the article cites Barnes’ Notes on the New Testament (1974) in support, as it apparently states, “It cannot be absolutely certain that the writer meant to refer to the Lord Jesus specifically here… There is no real incongruity in supposing, also, that the writer here meant to refer to God as such.” Thus, the JWs feel justified in adding the word ‘Jehovah’ before ‘God’ in their New World Translation of Rev. 1:8. citing 7 translations dating from 1599 to 1961. [See their 1969 KIT for that.]
(2) ‘Insight Vol. I’ also acknowledges an “additional occurrence of this phrase in the King James rendering of Rev. 1:11”. But the JW view is that some Greek manuscripts, including the Alexandrine, Sinaitic, and Codex Ephraemi rescriptus, do not have the trumpet sounding “I am the Alpha and Omega, the first and the last”. They therefore omit this, as do many other modern translations, which is possibly why you did not include verse 11 in your question.
The ‘Insight’ book then goes on to deal with Rev. 21:6 where it says “I am the Alpha and Omega, the beginning and the end,” dismissing that as applicable to Jesus because verse 7 adds, “and I shall be his God and he will be my son”. JW theology acknowledges Jesus as the Mighty God of Isaiah 9:6, but refuses to have him elevated from what they take to be a secondary level of deity, to a God who is to be worshipped. See Isaiah’s Prophecy Vol. I pp130-131 (published 2000). The ‘Insight’ book, however, does not say that but gives as its reason for applying verse 6 to Jehovah:
“Inasmuch as Jesus referred to those who are joint heirs with him in
his Kingdom as ‘brothers’, not ‘sons’, the speaker must be Jesus’
heavenly Father, Jehovah God.” (The JW link above agrees with this.)
You particularly want to know how “the eternality” of Jesus Christ (John 1:1-3) relates to Jesus being the first and the last. It is common knowledge that the NWT renders John 1:1 as ‘the Word was a god’, meaning the Word cannot be of the same Being as God. JWs do not believe in “the eternality” of Jesus Christ and so offer an interpretation of him being ‘the first and the last’ that only refers to his unique, one-of-a-kind resurrection. This is why JW doctrine, that the Word was created by Jehovah and so had a starting point in time, has to be explained as only referring to Jehovah raising Jesus to life in a unique way (as the ‘first fruits’ of those who sleep in death), and that as nobody else will be so resurrected, Jesus is ‘first and last’ in that sense only.
Isaiah 44:6 is dealt with in the JW book “Isaiah’s Prophecy” Vol. II pp64-65 (published 2001). It is not quoted in isolation but includes verses 7 & 8 to give context. Then the paragraph following explains how Jehovah is challenging the [false] gods to present their case, adding,
“Only ‘the first and the last,’ who existed before all the false gods
were thought of and will still be there when they are long forgotten,
can do such a thing. His people need not fear to bear witness to this
truth, since they have the support of Jehovah, who is as firm and
stable as a massive rock!”
It does not say a word about Jesus. That would fit in with the JW stance that Jesus being ‘first and last’ is only with respect to his unique resurrection – something that happened TO him, and not due to his BEING the first and the last. As JWs insist that only Jehovah is eternal (with no starting point in time) they agree he is eternal in his un-created being, but that Jesus is a created (hence, different) being: “The Bible applies this term both to Jehovah God and to his Son, Jesus, but with different meanings” as that first JW link says. I give this answer purely to answer your question, without agreeing with the JW stance.