Apollos’ early status (Acts 18-19)

There is a textual variant with reference to Apollo's knowledge of Jesus.  This could be the difference, if he knew more than the 12 disciples of John, and he only needed informed about the death and resurrection having been fulfilled.

Those who are seriously committed and zealous in the word will respond positively in short order when given clarification in the word of God.

The reception of the Spirit could be no more than receiving spiritual gifts that for Jews had to be clearly in connection with faith in Christ, and therefore, unlike Cornelius, this manifestation came after baptism. 

Jews and Samaritans had to "received" the Spirit after baptism in Christ's name and after apostolic recognition to make it certain it was in connection with faith in Christ and not merely because of their association with the Jewish or Samaritan religion.

This view requires a distinction between regeneration and receiving the Spirit.

There has to be something different about these situations when compared to Gentile salvation as in the case of Cornelius who received the Spirit the moment he believed and before Baptism in Acts 10.43-48--which is held to be the normal Christian experience.

It seems in all these accounts that receiving the Spirit is associated with Christ being believed in, or through baptism in connection with Christ, or through contact with an Apostle of Christ.

The disciples of John were surely informed of the coming of Christ and the baptism of the Holy Spirit, and they had believed in Him according to the message of John.  It's possible they did not know specifically about Jesus being the Christ. They did not know the Spirit was given in the capacity prophesied.  The baptism of repentance was a call to get right with God in anticipation.

 They may have left before Jesus appeared on the scene.  It would seem odd that they didn't know all that occurred since that time with Jesus, but where they had been may have kept them isolated.

Apollos was eloquent and mighty in the Scriptures, taking the message of John to the synagogues.  He surely was an OT believer in the coming Savior. The Greek text of the KJV says he spoke of the Lord, but the Greek of the Alexandrian says he spoke of Jesus--was this actual knowledge or prophetic knowledge?  His message was accurate, but Aquila and Priscilla had a fuller revelation based on what had transpired in the person of Jesus.  They had more accurate info to dispatch to Apollos. He may have learned from Disciples of John in Alexandria.

There's no reference to Apollos being baptized or receiving the Spirit here.

He obviously received it most readily, which shows his handle on the word of God and the faith he already possessed.  He took the further revelation and ran with it--to Corinth in Achaia.

That repentance can precondition or facilitate faith in Christ is seen in the response of both Apollos and the 12 disciples of John.  Both responded positively to the further revelation.

Apollos ministry in Corinth was a grace message:  he comforted through grace, though this particular grace could refer to Apollo's gift.  But consider:  "Now when the congregation had broken up, many of the Jews and devout proselytes followed Paul and Barnabas, who, speaking to them, persuaded them to continue in the grace of God."  Acts 13:43.