Is it permissible for someone to make a supplication to Allah to marry an already married, or an engaged woman?
No, it isn`t, and the person who does so is sinful before Allah, The Almighty.
Is committing Zina (Adultery and extramarital sex) without the intention of getting pregnant or deflowered considered full Zina?
All perfect praise be to Allah the Lord of the Worlds. May Allah`s peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
The Messenger of Allah (PBUH) says: "The eyes commit fornication, the hands, the feet, and the private parts." [Musnad Ahmad, P.3912]. Sheikh Shu`aib `Arn`oot graded this Hadith as sound. What you are asking about is far graver. Generally speaking, sincere repentance erases sins, good deeds erase bad deeds, and fearing Allah stops one from committing this heinous act. In addition, the devil is man`s worst enemy and whoever surrenders themselves to the wolf will be eaten. And Allah The Almighty Knows Best.
Are dream interpretation books accurate?
All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon Prophet Mohammad and upon all his family and companions.
Dream interpretation books are unreliable because they are merely expectations, not rulings of Sharia. However, if one sees a dream which one does not like, one should spit on one's left side and seek the refuge of Allah from the satan; it will not do one any harm, and one should not disclose it to anyone. If one sees a good vision, one should feel pleased but should not disclose it to anyone but whom one loves. And Allah The Almighty Knows Best.
Are phone conversations between the two sexes permissible if for consultation, and within the limits of good manners?
Such act is impermissible since it renders hearts corrupt, and could lead to forbidden attachment. Allah, The Almighty, Says (What means): "and follow not the footsteps of the devil." [Al-Baqarah/68].