Is the husband liable to provide for his wife and children if they are living separately?

Q: My sister is in Canada, married with 2 kids (age 11 and 2), and as per her marital difference and diffculties they both husband wife decided to live separate for few months to see if they can bring sulah in between them. In the mean time, the kids staying with the mother. As, per sharia law what will be husband and wife's responsibilities as far as naan/nafkhaa is concern for mother and kids? Does mother have to go to work to take care of house and kids where she will be living for this few months? Or husband will have to provide something from his side to support two kids and wife?

Making cuts on one's body

Q: Want to ask you that there is a person he or she self harms means he or she makes cuts on his or her body. Everytime he or she says that it's the last time but the next time he or she does the same thing again and again. What does islam says about this? Will Allah Ta'ala forgive? What will be the punishment for it?

Explanation of the statement of Hazrat Umar (radiyallahu anhu), "Do not let the prayer of a man deceive you nor his fasting..."

Q: What is the meaning of this narration: Sayyiduna ‘Umar ibn Al Khattab (radiyallahu ‘anhu) said: “Do not let the prayer of a man deceive you nor his fasting. Rather look at the truthfulness of his speech, his trustworthiness whenever he is entrusted, and how he acts whenever he is given wealth/power.”

Imams Musaddad, Bayhaqi (rahimahumallah) and other Muhaddithun have recorded this statement of Sayyiduna ‘Umar ibn Al Khattab (radiyallahu ‘anhu). Hafiz Ibn Hajar Al ‘Asqalani (rahimahullah) has declared the narration authentic. (Shu’abul Iman, Hadith: 4898 and Al Matalibul ‘Aliyah, Hadith: 2631)

Forgetting to sit for the last qa'dah

Q: A person was performing a four rakaat fardh salaah. After performing the fourth rakaat, he did not sit for the qa'dah but forgetfully stood up for the fifth rakaat. He then made ruku and sajdah in the fifth rakaat, sat for tashahhud and made salaam.

What is the status of his salaah? Is his fardh salaah valid or does he have to repeat his salaah?