What Had to Precede Pentecost?

Not sure why you think there were specifically six things.

In any event, there are a number of key events, though several are collectively known as one dramatic event in salvation history.

First, according to the divine plan, the Second Person of the Holy Trinity had to become man, Jesus Christ (Jn. 1:1-3, 14), and live out his earthly ministry. Indeed, God’s saving plan begins with the Incarnation (CCC 461ff.).

Second, Jesus had to suffer and die on the Cross for our sins, so that we might have new life in him.

Third, Jesus had to rise from the dead in triumph over sin and death (1 Cor. 15:12-22).

Fourth, Jesus had to ascend to heaven to complete his Paschal Mystery, i.e., his one Sacrifice of Calvary that encompasses his Passion and Death, Resurrection, and Ascension into heaven (Jn. 20:15-18; Heb. 9:11-14; CCC 1085), so that the Father would send the Holy Spirit (Jn. 14:15-31; 16:4-11).

For more on the importance of Pentecost, see my article “Pentecost and the Papacy.”