Is it permissible to swear by (Allah "The Living")?
Yes, it is permissible because "The Living" is one of Allah`s Attributes.
Is it permissible to offer Tahajjud prayer after Witr prayer?
It is permissible to offer voluntary prayer after Witr (An odd number prayer performed between Isha and Fajr) prayer. However, it is desirable that the night prayer be ended with Witr. Therefore, it is desirable for one, who thought that he was most probably going to wake up at night in order to offer Tahajjud, to offer Witr after it, but one, who fears that he might not wake up, should offer Witr before going to bed.
Ruling when Husband Utters Divorce Jokingly, or in the State of Intoxication or Anger
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 man who utters divorce while in the state of anger, his divorce doesn`t take place and the same ruling applies to the man who is forced to utter divorce because he is threatened to be killed or one of his organs cut off, in addition to other matters that scholars have mentioned in this regard. However, the man who utters divorce jokingly or while having intentionally drunk alcohol, his divorce takes place. And Allah The Almighty Knows Best.
Are minors obliged to fast?
A male under the age of puberty isn`t required to fast, but his guardian should order him to fast if he was able to endure the hardship until being used for fasting in general. And Allah Knows Best.