Verses 4 - 7 provide us with an interpretative key: Approaching Revelation as a Liturgy yields abundant fruits. An important principle that will be often repeated is that Catholics cannot separate the Liturgy from the rest of their week because the Lord of Heaven and earth does not.
We learn more about faithful and unfaithful witnesses by reflecting on the roles that Adam, Judas, St. John the Baptist, and St. John the Evangelist played in the life of Christ.
How does God have mercy on us? Through the Liturgy.
How does God shower us with grace? Through the Mass.
Is Jesus the King of Christians only?
How are we to love our brothers and sisters? Hint: think Liturgy.