1-The Hadith which reads “Fasting on one of these days (the first ten days of Dhul-Hijjah) is equivalent to fasting for a year” has a da‘if isnad (weak chain of transmission) because of an-Nahhas ibn Qaham and and Mas‘ud ibn Wasil
2- The hadith which reads “There are five things that the Prophet (peace and blessings of Allah be upon him) never failed to do…” is based on the report narrated by Hunaydah ibn Khalid al-Khuza‘i, from whom it was narrated via many isnads, in several versions. The critics of hadith differed as to the classification of this hadith because each of these versions has its own isnad and text. For more, see the detailed answer.

1. According to the view of the majority of scholars, it is encouraged (mustahabb) to fast the first nine days of Dhul-Hijjah.
2. There are several scholarly opinions concerning the hadeeth of ‘Aishah according to which the Prophet (blessings and peace of Allah be upon him) did not fast these ten days. Please see the detailed answer for these views.

1- Fasting on the first eight days of Dhul-Hijjah is recommended for pilgrims and others.
2- It is not Sunnah for pilgrims to fast on the day of ‘Arafah, rather it is recommended for them not to fast, even if they are able to fast.

1-The ten days of Dhul-Hijjah are among the great seasons of worship which Allah has favoured over other days.
2-So, the Muslim should start these days with sincere repentance to Allah, then he should do a lot of righteous deeds in general, then he should pay attention to doing the following deeds: observing fasting, reciting tahmid, tahlil and takbir, offering Hajj, ‘Umrah and Udhiyah. For more, see the detailed answer below.

1. If a wife makes a vow to fast the first nine days of Dhul-Hijjah on a permanent basis, it is a vow to do an act of obedience and she is obliged to fulfill it.
2. The husband does not have the right to prevent her from doing that, because her husband may only prevent her from observing voluntary fasts. Please see the details below.

1-There is no proof for any particular event having occurred during the first ten days of Dhul-Hijjah. Rather these are hadiths that are falsely attributed to the Messenger of Allah (blessings and peace of Allah be upon him).

2-The virtue of the first ten days of Dhul-Hijjah and of doing righteous deeds during them, especially fasting, is proven in the saheeh hadiths.

3-The fact that a day is proven to be of virtue does not necessarily mean that any important event happened on that day; rather it is sufficient to note that Allah has favoured this day above others.

It is recommended to fast nine days of Dhul-Hijjah. The tenth day of Dhul-Hijjah is the day of ‘Eid which is prohibited to fast. What is meant by the virtue of fasting the ten days of Dhul-Hijjah is fasting nine days only, even though they are called ten days.

1- Unrestricted Takbir (mutlaq) is not limited to a specific time, and it is Sunnah to say it all the time, morning and evening, before prayer and after prayer, at all times. Restricted Takbir (muqayyad) is limited to the time immediately after prayer.
2- It is Sunnah to recite unrestricted takbir during the first ten days of Dhul-Hijjah and all the days of Tashriq, starting from the beginning of the month of Dhul-Hijjah (i.e., from sunset on the last day of Dhul-Qi’dah) until the end of the days of Al-Tashriq, which is when the sun sets on the thirteenth day of Dhul-Hijjah).
3-With regard to restricted takbir, it starts from Fajr on the day of ‘Arafah and lasts until the sun sets on the last day of the days of Tashriq.
4-The scholars have different views on the formulas of Takbir which are explained in the detailed answer.

Takbir in unison before ‘Eid prayer is an innovation because there is no evidence for it, and the Prophet (peace and blessings of Allah be upon him) said: “Whoever does an action that is not part of this matter of ours will have it rejected.” What `Umar (may Allah be pleased with him) did is not evidence for reciting takbir in unison; rather what `Umar (may Allah be pleased with him) did was to say takbir by himself, and when the people heard him they said takbir, each one by himself. This does not indicate that they all said takbir in unison.