What does it mean when it says that God is a spirit and we must worship him in spirit?

Please give me a study report about the virgin birth (Isaiah 7:14) and its fulfillment in the New Testament.

The Bible states that God "predestines" Christians for a future with Christ in Heaven and that he does NOT predestine others to Hell; however, does this mean that only a few of the Christians on Earth were predestined by God and the rest "happened" to come to Christ by the work of these Christians and the Holy Spirit? Or were ALL the people who God knew would become Christian through His omniscience thus "predestined" by Christ?

I have a question. To whom am I supposed to pray? I believe in it, but who am I suppose to pray if I want to repent and be saved? our heavenly father or Jesus? or does it make any difference?

When the Great Tribulation comes, how can people be saved? Is it still by faith or plain works?

Are the ten commandments God's Law handed down? Are they never changing? Do they still apply to this day and age?

When a man dies, where does the spirit go? If the "spirit" of man is the one that gives the believer the knowledge of God, then does the "spirit" of an unbelieving man have knowledge of God?

Please define and explain the characteristics of the soul and the spirit of man.

What does the Bible teach concerning slavery and servanthood? Is it always considered an ungodly practice or are there situations where servanthood is scriptural?

Will God, through the Holy Spirit, finally give up on calling someone for salvation, if the person continues to reject the call?