You presented the following quote allegedly attributed to Joseph Smith:
ďChrist is the firstborn spirit Son in the eternal family, and while yet in pre-existence he advanced and progressed and became like the Father in power and intelligence; that is, he became a God
That is indeed a very interesting quote. I do not know the original specific reference source from which you obtained the quote. Could you please identify that source so I may review it in proper context?
It is certainly possible that Joseph Smith made such a statement.
For starters, one might examine some reasons that might elicit such a declaration.
Is the fullness of becoming a God to be understood as a singular event?
Or is it a process of eternal progression?
First one should ask, did Christ embody His complete stature and fulness in the Godhead in the beginning or thousands of years later? Consider what Luke said regarding the young Jesus:
Luke: 2:52 And Jesus increased in wisdom and stature, and in favour with God and man
Consider also Christís own testimony as found in:
John 5:19 Then answered Jesus and said unto them, Verily, verily, I say unto you, The Son can do nothing of himself, but what he seeth the Father do: for what things soever he doeth, these also doeth the Son likewise
In other words Christ has only done what he has seen the Father do.
We should also observe that Christ himself was subject unto the Father as shown in:
1 Corinthians 15:28 And when all things shall be subdued unto him, then shall the Son also himself be subject unto him that put all things under him, that God may be all in all
We should remember that according to scripture Christ obtained not a fulness at first, but continued from grace to grace until he obtained a fulness. It is most obvious that he could not receive a fulness until His mission was completed by partaking of that bitter cup as He submitted his will to the will of the Father by completing the atonement for the redemption of all who would come unto him through faith and repentance.
Let us examine this in the light of Christís antemortal, mortal and post mortal states.
First let us examine what is stated in:
Revelation 12:7 And there was war in heaven: Michael and his angels fought against the dragon; and the dragon fought and his angels, 12:8 And prevailed not; neither was their place found any more in heaven.
12:9 And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him.
12:10 And I heard a loud voice saying in heaven, Now is come salvation, and strength, and the kingdom of our God, and the power of his Christ: for the accuser of our brethren is cast down, which accused them before our God day and night.
We observe in the above that John the Revelator beheld in vision some of the scenes that had been enacted in the spirit-world before the beginning of human history. We observe specifically that Christ was apparently foreordained to become the power by which salvation would come.
It is our understanding that Christ was foreordained to become our redeemer as shown in:
1 Peter 1:18 Forasmuch as ye know that ye were not redeemed with corruptible things, as silver and gold, from your vain conversation received by tradition from your fathers; 1:19 But with the precious blood of Christ, as of a lamb without blemish and without spot: 1:20 Who verily was foreordained before the foundation of the world, but was manifest in these last times for you.
It is obvious that if he was foreordained then one (Eloheim), who stood as the ďmost highĒ was required to ordain him.
We observe also in:
Matt. 15:24 But he answered and said, I am not sent but unto the lost sheep of the house of Israel
If he was ďsent
Ē then one higher in seniority must have sent him.
In another place Jesus said:
John 7:33 Then said Jesus unto them, Yet a little while am I with you, and then I go unto him that sent me
Again it appears that God the Father had power to send Jesus.
We observe also that according to:
Hebrews 5:5 So also Christ glorified not himself to be made an high priest; but he that said unto him, Thou art my Son, to day have I begotten thee
Obviously the Father had a level or seniority over that of His only begotten Son.
Also, if he (Christ) was in the position of being God the Father he would have no need to be tested as shown in:
Hebrews 4:15 For we have not an high priest which cannot be touched with the feeling of our infirmities; but was in all points tempted like as we are, yet without sin
Some also take exception to the fact that we we also believe that Christ is the ďfirst born
Ē, for we truly do believe such. For so also do the scriptures so testify.
Psalms 89:26 He shall cry unto me, Thou art my father, my God, and the rock of my salvation.
Psalms 89:27 Also I will make him my firstborn, higher than the kings of the earth
Psalms 89:28 My mercy will I keep for him for evermore, and my covenant shall stand fast with him.
Psalms 89:29 His seed also will I make to endure for ever, and his throne as the days of heaven
Isaiah 41:4 Who hath wrought and done it, calling the generations from the beginning? I the LORD, the first, and with the last; I am he
John 1:1 In the beginning was the Word, and the Word was with God, and the Word was God.
Also we observe what Paul said in:
Romans 8:29 For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren
Observe also what Paul stated in:
Col. 1:15 Who is the image of the invisible God, the firstborn of every creature
Further Paul stated in:
Hebrews 1:1 God, who at sundry times and in divers manners spake in time past unto the fathers by the prophets, 1:2 Hath in these last days spoken unto us by his Son, whom he hath appointed heir of all things, by whom also he made the worlds; 1:3 Who being the brightness of his glory, and the express image of his person, and upholding all things by the word of his power, when he had by himself purged our sins, sat down on the right hand of the Majesty on high: 1:4 Being made so much better than the angels, as he hath by inheritance obtained a more excellent name than they
1:5 For unto which of the angels said he at any time, Thou art my Son, this day have I begotten thee? And again, I will be to him a Father, and he shall be to me a Son? 1:6 And again, when he bringeth in the firstbegotten into the world, he saith, And let all the angels of God worship him
We should observe from the above that God the Father had appointed his son to be:
1. heir of all things,
2. that by his Son the worlds were made,
3. that Christ was express image of his person,
4. had purged our sins,
5. sat down on the right hand of the Majesty on high,
6. by inheritance obtained a more excellent name,
7. He (christ) is identified as the first begotten who was also later brought into the world i.e. ďAnd again, when he bringeth in the first begotten into the world
Consider also that which was spoken by Paul to the Hebrews:
Hebrews 12:22 But ye are come unto mount Sion, and unto the city of the living God, the heavenly Jerusalem, and to an innumerable company of angels, 12:23 To the general assembly and church of the firstborn, which are written in heaven, and to God the Judge of all, and to the spirits of just men made perfect
The above are just a few of the things which may in part have justified such a statement as you have quoted in part from and undeclared source.
As I stated in the beginning I may not give a full account until you identify the original source of your quotation that I might review the same in itís full context.