Luke 24:44-45:
And he said unto them, These [are] the words which I spake unto you, while I was yet with you, that all things must be fulfilled, which were written in the law of Moses, and [in] the prophets, and [in] the psalms, concerning me. Luke 24:44
Then opened he their understanding, that they might understand the scriptures, Luke 24:45
What then did Jesus mean by "all things"? It is that which was concerning Him, "while [he] was yet with [them]"?
When was He, Jesus the Christ, with them?
During His First Advent.
What then did Jesus mean, when He said that He opened their understanding in the scriptures, in the Law of Moses, the Prophets, and the Psalms concerning Him?
Contextually, it is that which was written to be fulfilled of His First Advent...
See Luke 24:46-48 [context], speaks of Christ's suffering, rising from the dead the third day [1st Advent language], and repentance and remission of sins to be preached [still 1st Advent language, for in the 2nd Advent [nor 3rd] no such thing will be done any more], and witnesses of these things [1st Advent witnesses]].
And said unto them, Thus it is written, and thus it behoved Christ to suffer, and to rise from the dead the third day: Luke 24:46
And that repentance and remission of sins should be preached in his name among all nations, beginning at Jerusalem. Luke 24:47
And ye are witnesses of these things. Luke 24:48
And, behold, I send the promise of my Father upon you: but tarry ye in the city of Jerusalem, until ye be endued with power from on high. Luke 24:49
What promise was that? The promise of the Holy Spirit, even as it was foretold in scripture by prophecy and typologically [Exodus 29:7; Leviticus 8:12; Psalms 133, etc]. This had not yet been fulfilled either, for in Acts 2:1, we see that the Great Day of the True Pentecost was "fully come". Iow, then fulfilled [after Christ Jesus death on the Cross and Resurrection and 2nd Ascension, - Mt. Olivet] by what transpired in Heaven. Christ Jesus became the Great Highpriest, and the Head of the Body anointed there for the daily service in the Holy Place of the Heavenly Tabernacle. For we see in Acts 1:20 that something had not yet been fulfilled in regards to Jesus, for there needed to be 12 [Exodus 28:21-22, 29:5, 39:14] before He continued, [for at that time only 11 remained, thus the 12th, Matthias was chosen of God [Acts 1:26], being "numbered" with the other 11] :
For it is written in the book of Psalms, Let his habitation be desolate, and let no man dwell therein: and his bishoprick let another take. Acts 1:20
For this too needed to be "fulfilled" [Acts 1:16], since the first portion, the removal and end of Judas, was.
Continuing onward, it also reveals that more was still to be fulfilled about Christ Jesus:
And it came to pass, while he blessed them, he was parted from them, and carried up into heaven. Luke 24:51
This was foretold, in Psalms 24.
Who shall ascend into the hill of the LORD? or who shall stand in his holy place? Psalms 24:3
Lift up your heads, O ye gates; and be ye lift up, ye everlasting doors; and the King of glory shall come in. Psalms 24:7
Who [is] this King of glory? The LORD strong and mighty, the LORD mighty in battle. Psalms 24:8
What Battle was Jesus victorious in?
The Battle with Satan at the Cross, even as Revelation 12:10, etc reveals, "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."
Lift up your heads, O ye gates; even lift [them] up, ye everlasting doors; and the King of glory shall come in. Psalms 24:9
Who is this King of glory? The LORD of hosts, he [is] the King of glory. Selah. Psalms 24:10
It had not yet taken place, and even Revelation 12:5, reveals "...child was caught up unto God, and [to] his throne...".
Jesus was then to be anointed as Great High Priest and send forth the Holy Spirit as promised:
And I beheld, and, lo, in the midst of the throne and of the four beasts, and in the midst of the elders, stood a Lamb as it had been slain, having seven horns and seven eyes, which are the seven Spirits of God sent forth into all the earth. Revelation 5:6
See Psalms 133:1-3.
[[A Song of degrees of David.]] Behold, how good and how pleasant [it is] for brethren to dwell together in unity! Psalms 133:1 [see "And when the day of Pentecost was fully come, they were all with one accord in one place." Acts 2:1]
[It is] like the precious ointment upon the head, that ran down upon the beard, [even] Aaron's beard: that went down to the skirts of his garments; Psalms 133:2 [Holy Spirit poured out upon Christ Jesus our Head in Heaven, and ran down unto the body, even unto the feet, and the feet will be the remnant...]
As the dew of Hermon, [and as the dew] that descended upon the mountains of Zion: for there the LORD commanded the blessing, [even] life for evermore. Psalms 133:3
"All", in Luke 24:44 is subject to context, it speaks of "all" that which pertained unto the contextual events mentioned therein as seen above.
Therefore, Jesus did not fulfill "all" [every last prophecy], yet, since He had a work to do in the Heavenly as our Great High Priest, and all the events surrounding it, as well as His coming as King of Kings and Lord of Lords, etc. Even moreso, we could look at Luke 24:44, as saying that "all" [everything], "must be" [as in meaning, it still remains for some things to be] fulfilled concerning Jesus, and all is not yet so done, but Jesus opened the scriptures and showed them that which had up to that point been fulfilled concerning Him.
"All" is subject to context, even as it "always" is.