I'll take "4," Regis. Final Answer.
Purgatory is a state where the "saved" (those destined for Heaven) are purified or "purged" of the remnants of their selfish, un-Godly selves. This purgation is necessary before entrance to Heaven, as nothign unclean can come into the presence of God. (Think of the Isaiah passage where the angel uses a hot coal to "purify" Isaiah's lips.)
If our goal in life is to use the power of Christ to "Become perfect, as God is perfect," we can not all acheive this goal while on earth. So our "perfection" is completed on the way to Heaven. The power of Christ acheives all.
SD