Yes, Christ was perfect before this time. The Law of God not only forbids us from doing certain, but it commands us to do certain things. That is why we cannot live up to God's standard...as the Psalmist said, "I have seen a limit to all perfection; Your commandment is exceedingly broad" (119:96).

Why did Christ fulfill all righteousness?

Isaiah explains for us:

Quote
4 Surely our griefs He Himself bore,
And our sorrows He carried;
Yet we ourselves esteemed Him stricken,
Smitten of God, and afflicted.
5 But He was pierced through for our transgressions,
He was crushed for our iniquities;
The chastening for our well-being fell upon Him,
And by His scourging we are healed.
6 All of us like sheep have gone astray,
Each of us has turned to his own way;
But the LORD has caused the iniquity of us all
To fall on Him.
7 He was oppressed and He was afflicted,
Yet He did not open His mouth;
Like a lamb that is led to slaughter,
And like a sheep that is silent before its shearers,
So He did not open His mouth.
8 By oppression and judgment He was taken away;
And as for His generation, who considered
That He was cut off out of the land of the living
For the transgression of my people, to whom the stroke was due?
9 His grave was assigned with wicked men,
Yet He was with a rich man in His death,
Because He had done no violence,
Nor was there any deceit in His mouth.
10 But the LORD was pleased
To crush Him, putting Him to grief;
If He would render Himself as a guilt offering,
He will see His offspring,
He will prolong His days,
And the good pleasure of the LORD will prosper in His hand.
11As a result of the anguish of His soul,
He will see it and be satisfied;
By His knowledge the Righteous One,
My Servant, will justify the many,
As He will bear their iniquities.
12 Therefore, I will allot Him a portion with the great,
And He will divide the booty with the strong;
Because He poured out Himself to death,
And was numbered with the transgressors;
Yet He Himself bore the sin of many,
And interceded for the transgressors (53:4-12).

It was so the many would be justified. While here the sacrificial aspects are highlighted, Isaiah elsewhere says:

Quote
10 I will rejoice greatly in the LORD,
My soul will exult in my God;
For He has clothed me with garments of salvation,
He has wrapped me with a robe of righteousness,
As a bridegroom decks himself with a garland,
And as a bride adorns herself with her jewels.
11 For as the earth brings forth its sprouts,
And as a garden causes the things sown in it to spring up,
So the Lord GOD will cause righteousness and praise
To spring up before all the nations (61:10-11).

Jeremiah also says that, in the days of the Messiah, the saved will call God by the name "The LORD our righteousness" (23:6, 33:16).

True godliness is a sincere feeling which loves God as Father as much as it fears and reverences Him as Lord, embraces His righteousness, and dreads offending Him worse than death~ Calvin