Question. (i) Can a man/woman remove his hair (hands, legs, chest, back). If the answer is no, please provide me a reason. (ii) Should we remove our hair before 40 days?

Answer. In the name of Allah, Most Gracious, Most Merciful
1) It is permissible for both men and women to remove unwanted hair from areas such as the hands, legs, chest, and back. However, it is undesirable for them to do so. It is not permissible to trim the eyebrows and for women to remove hair from the head.
Rasulullah (Sallallahu Alayhi Wasallam) has cursed women who trim and shape their eyebrows. It is said in a Hadith:
عن علقمة قال لعن عبد الله الواشمات والمتنمصات والمتفلجات للحسن المغيرات خلق الله فقالت أم يعقوب ما هذا ؟ قال عبد الله وما لي لا ألعن من لعن رسول الله وفي كتاب الله ؟ قالت والله لقد قرأت ما بين اللوحين فما وجدته قال والله لئن قرأتيه لقد وجدتيه { وما آتاكم الرسول فخذوه وما نهاكم عنه فانتهوا{
"Abdullah cursed those women who practiced tattooing and those who removed hair from their faces and those who created spaces between their teeth artificially to look beautiful. Such ladies have changed what Allah has created. Um Yaqub said, "What is that?" Abdullah said, "Why should I not curse those who were cursed by Allah's Messenger and are referred to in Allah's Book?" She said to him "By Allah, I have read the whole Quran but I have not found such a thing. Abdullah said, "By Allah, if you had read it (carefully) you would have found it. (Allah says:) 'And what the Prophet gives you, take it and what he forbids you, abstain (from it).'" - (Sahih Al-Bukhari 7/83 Dar al-Fikr)
وفيه: قطعت شعر رأسها أثمت ولعنت زاد في البزازية: وإن بإذن الزوج لا طاعة لمخلوق في معصية الخالق
(Darrul-Mukhtaar, 6/407, HM Sa'eed)
وفي حلق شعر الصدر والظهر ترك الأدب كذا في القنية
(Raddul Muhtar, 6/407, HM Sa'eed)(Bahishti Zewar, 2/81-82, Zam Zam Publishers) (Fatawa Mahmudiyya, 19/444, Faruqiyya)
2) It is necessary to remove pubic hair and hair of the underarms within a period that does not exceed forty days. If one does not do so within forty days, it will constitute as a sin.
(Bahishti Zewar, 2/82, Zam Zam Publishers)

Question. Kindly let me know what Islam says about interfaith marriages? e.g christian girl - muslim man.

Answer. In the name of Allah, Most Gracious, Most Merciful
At the outset it should be understood that marriage is an important step and a lifelong responsibility. Realising the responsibility of such a major decision, one should select a suitable partner to fulfil this great Sunnat of Rasululah (Sallallahu Alaihi Wasallam).
حدثنا مسدد حدثنا يحيى يعنى ابن سعيد حدثنى عبيد الله حدثنى سعيد بن أبى سعيد عن أبيه عن أبى هريرة عن النبى صلى الله عليه وسلم قال تنكح النساء لأربع لمالها ولحسبها ولجمالها ولدينها فاظفر بذات الدين تربت يداك
It has been narrated from Abu Huraira (RA) that Nabi (Sallallahu Alaihi Wasallam) said "Women are married for four reasons. (She is either married) for her wealth, for her lineage, for her beauty and for her Deen. Then be successful by (taking) a woman of Deen, (Otherwise) may your hands be soiled."
From the above Hadith, the importance of giving Deen preference when selecting a partner for marriage is understood.
Shari'a encourages Kufu (suitability/compatibility) between the spouses in marriage. This compatibility is emphasized in Shari'a in the interest of both parties, as the spouses intend to be together forever. For a successful marriage they will have to be thinking and living alike, and this would only be achieved by having compatibility between them. After all, the purpose of marriage is to live in tranquillity and peace with a suitable spouse. If this is not achieved, the purpose of marriage would be defeated. A contributing factor to the breakup of marriages is the different outlook of either spouse, be it social, moral or religious.
Marrying a Christian or Jewish spouse poses many challenges. One of the biggest challenges in such marriages is the rearing of children. If the spouses should have children, each of them would want the child or children to follow their respective religions. Automatically this will cause an argument. If the husband is weak in his Deen, he will succumb to the desire of his wife and their children will perhaps end up going to church. Not only will the child be influenced in this way but the wife will take the child to her parents where the child will get used to their way of life and even end up eating non Halaal foods. Even worse would be the case where those grandparents actually influence the child against his or her own father because of dislike for his religion. The children in such a marriage sometimes grow up confused not knowing what to follow as they had seen their father practicing on one Deen and the mother practicing something else. By not having a sound upbringing, their whole life and their concept of marriage will be corrupted. In this case, the children cannot be blamed; rather this is the consequence of the negative atmosphere they were exposed to and the incompatibility of the parents. Sadly, in most cases, these marriages end in divorce. Many families have broken up in this way causing a ripple of social disruption; causing innocent children to suffer the unfortunate consequence.
In some cases the father is strong in his Deen and will have the upper hand over his children. Having a strong influence on the child and sometimes even on his wife.
If you acquainted with a Christian girl, it would be an extremely meritorious act to encourage her to embrace this Deen of Islam. However, this will be no easy task as there will be much for her to learn and sometimes, in some cases, if she embraces Islam only to make the husband happy, she may decide that Islam is not the way of life she had in mind and decides to leave this Deen.
On the other hand it would be highly advisable to marry a good Deeni girl who would not only be a wonderful wife but an excellent mother. She would be such a wife who would be regular on her Salaah and also encourage her children to perform Salaah; a wife who would give her children an Islamic upbringing and good manners and most of all, a wife who would treat her husband with respect and love. Therefore, ponder carefully over your decision.
And Allah knows best