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.

There are six conditions for the udhiyah: 1- It should be one of the an'am class of animals; 2- It should have reached the age stipulated in Shari’ah; 3- It should be free of any faults that would render it unsuitable for sacrifice; 4- The animal should belong to the person who is offering the sacrifice; 5- No one else should have any rights to the sacrificial animal; 6- It should be slaughtered at the time specified in Shari’ah

1. Udhiyah means an animal of the an’aam class (i.e., camel, cow, sheep or goat) that is slaughtered during the days of ‘Eid al-Adha.

2. Udhiyah is one of the rituals of Islam prescribed in the Book of Allah and the Sunnah of His Messenger (peace and blessings of Allah be upon him), and according to the consensus of the Muslims. Please see the detailed answer for more about the rulings on udhiyah.

The Shar`i evidence indicates that a sheep that has reached the age of six months may count as a sacrifice, as may a goat that has reached the age of one year, a cow that has reached the age of two years, and a camel that has reached the age of five years. Sacrificing an animal that is younger than that is not permitted, but if an animal that is older than that is sacrificed, it is permitted and is better.

The command to give the meat of the udhiyah in charity is reported in a number of hadiths, as was the permission to eat some and preserve some. At the very least, a third of the udhiyah should be eaten, a third should be given as gifts and a third should be given in charity.

The time for offering the sacrifice begins after the ‘Eid prayer on ‘Eid al-Adha and ends when the sun sets on the thirteenth of Dhul-Hijjah.

Scholars have different views on the ruling of udhiyah. Most of the scholars are of the view that udhiyah is Sunnah, and is not obligatory.

According to the majority of scholars, if a person breaks their Wudu during Tawaf and leaves to relieve themselves, the Tawaf becomes invalid and must be restarted. This is the view of the Malikis and Hanbalis. However, the Hanafis and Shafi`is allow completion if the interruption is brief and continuity is maintained.