Jude provides four duties of maintaining faithfulness. First, the building upon faith ( i.e. doctrinal understanding and trust); second, praying in the Holy Spirit (what it is); third, keeping oneself in the love of God (frequently forgotten steps), and fourth, avoiding dangers.

Why John is given a vision of the reigning Lord in biblical symbols, rather than a true resemblance, and how each symbol shows the true attitude of worship in church or in personal devotion, serving as a tonic for real appreciation of Christ and communion with Him.

Jude urges God's people to defend the faith, warning of the stealth of errorists, and of how down the centuries they invent doctrines and attack the authority of Scripture. He also reveals their motives and points to how the battle must be fought. 

A trick question is put to Christ by the Pharisees in the hope of discrediting Him, to persecute  Him, but He confounds them with a disarming reply that imparts all we so much need to know about the kingdom of God, and how to enter it.

Nine revelatory and sign gifts of the Spirit given for the ministry of the Word while the Scriptures were being completed. What they were and how they were eventually given to all believers - in the Word (Ephesians 1.17-19). Also, the gifts of Romans 12.6-8.