1. What must a person do to experience Hell?
the "hell" is the second(-ary) appearance of the "death", while the "death" is the vitiation at large i.e. things like: fall from grace, unhappiness, desolation, sorrow, bother, stress, aggravation, heartache, suffering, pain, degradation, misery, derangement, penury, famine, degenerative diseases, pestilences, congenital ailment, deformation, disability, dying, etc.
Revelation 6:8 "I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him."
2. Why must Hell be permanent?
the painful punishment of God cannot be endless, because God is not unfair/unjust that to punish any villain more than it deserves, e.g. if a human stole something which costs ten cents then it would be unjust if the same be punished for 100 years in jail only because of ten cents, but how much more God would never punish any human more then it hurt/harmed?!
3. Why doesn't God allow those who desire it annihilation?
this question is not clearly formulated and i cannot understand what you exactly ask with it?!
4. Do you think it is possible to experience joy and pleasure in Hell?
it was possible till now, e.g. some people felt both [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse] and affliction during sex
5. How is the eternal suffering experienced by those in Hell justified in light of God's goodness?
to me this question is not clearly formulated too and cannot give an answer to it when i do not know what exactly you ask with it?!
but however the purpose of the true God is to provide complete salvation and abundant life to all humans/souls for the entire eternity, not to cause them a hurt/harm/perdition
Blessings