What is the age of the Aqiqa or the Udhiyah?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
The minimum age for a sacrificial animal (Udhiyah) and the birth sacrifice (Aqiqa) is as follows:
Camels: Five years old, entering their sixth year.
Cattle and Goats: Two years old, entering their third year.
Sheep: One year old, entering their second year; however, it is permissible for a sheep to be six months old provided it is large in size and plump.
And Allah the Exalted knows best.
Is it permissible for a mother to stop her daughter from marrying a respectable, God-fearing young man because he isn't college/university graduate?
It is impermissible to deny a woman her right in getting married except for a lawful reason, and problems can be solved through dialogue. However, she can file a suit in order for the judge to have a say in that regard.
Does buying meat equivalent to the weight of a slaughtered animal and distributing it avail for an udhiyah?
Praise be to Allah, and prayers and peace be upon our Master the Messenger of Allah.
That does not avail for the sacrifice (uḍḥiyyah), because the sacrifice necessarily requires slaughtering an animal from the category of anʿām (camels, cattle, and sheep/goats) within a specified time.
Rather, that is considered a form of charity (ṣadaqah) for which one is rewarded. And Allah Almighty knows best.
Is it incumbent on a father to cover the marriage costs of his son if the latter couldn`t afford them?
The son should seek the help of his relatives in order to convince his father to do the aforesaid, and the father should make sure that his son doesn`t commit fornication through helping him to get married, and Allah will reward him for doing so.