Does falling into sin indicate that there is something wrong with one's 'aqeedah (belief system)?

Allah tells us in the Qur'an not to cut off our blood relations. What is the interpretation of the Ayah that commands us not to severe ties of kinship? Who does it refer to? Just parents and siblings? What if one maintains contact with one's parents only through telephone or letters although he is capable of visiting them. Yet, he feels that maintaining a certain distance is healthier to the relationship ?

Is it permissible to ask the Muslims -when meeting with them- about the state of their faith or their hearts? One of them said to me that this is a matter of the unseen and that it is not appropriate to ask about it.

For how long does Allah forgive a person's sin? If he repents and seeks forgiveness from his sin, then goes and commits the same sin again, then he seeks forgiveness again then commits the same sin again, and so on, does Allah forgive him or does that mean that he is not sincere towards Allah, especially if he repeats that sin after a short while, but he does not stop seeking forgiveness?

I want to make my children keen to pray, because they will pray once then forget about prayer many times. I always advise them and pray to Allah to guide them. How can I encourage them and make them love prayer?.

Firstly: I apologize for asking such a question, and so that there will be no room for doubt about my intention I will say that I bear witness that there is no god but Allaah and that Muhammad is the Messenger of Allah, and I am completely content with Allah as my Lord, Islam as my religion and Muhammad (peace and blessings of Allah be upon him) as my Prophet.   

I am asking about the Sunnah, because there are many reports of a single hadith. For example, we may find in Saheeh al-Bukhaari a hadith that appears in a form different than that in which it appears in Saheeh Muslim. Why isn't the Sunnah like the Holy Qur'aan? What is the difference between the Sunnah and the Holy Qur'aan? Is the Sunnah part of the Wahy that was revealed to the Messenger (peace and blessings of Allah be upon him) or is it just his words and deeds? Is it one of the characteristics of Prophethood or what?

What is the ruling on mixing with kaafirs and dealing with them kindly, hoping that they will become Muslim?

Is it permissible to give charity to non-Muslims if they are in urgent need? Will the person who gives such charity be rewarded?

Is it permissible for me to say to non-Muslims "And the same to you" when they wish me a Happy New Year or say Best Wishes?

I am one of those who send blessings upon the Prophet between 50 and 100 times a day, according to circumstances. I say: “Allahumma salli ‘ala Muhammadin wa aali Muhammad (O Allah, send blessings upon Muhammad and the family of Muhammad).” There are some people who tell me that my sending blessings upon the Messenger of Allah is lacking. Can you tell us – may Allah reward you with good – what is the ideal way to send blessings upon the master of mankind, and is the way I am doing it really lacking?

There are many religions.

Why do Muslims think that Islam is true. Is there any factual basis?