1. Is providing breast milk for an infant Fard (for a baby too young to live on solid foods)? At what age (beyond two years) would breast-feeding become a Haram act?2. Is it Haram for children to pretend to be animals?

Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
1- There is no harm that children pretend to be animals imitating their movements or their voices, because Islam does not punish children for their acts as long as they have not reached the age of puberty. The evidence for this is the Hadith narrated by Al-Tirmizi that Prophet said: "The pen is lifted (prevented from writing the sins of these categories) from the sleeping person till he wakes up, the child till he becomes mature and from the mad person till he recovers his reason". Al-Tirmizi said that the meaning of this Hadith is used by the scholars of Islam.
So, the guardians of these children are not to prevent their children from performing such acts and playing in such a way because what the children do here does not lead to a forbidden act and the children like, by nature, to play and enjoy themselves.
On the other hand, we would like to draw your attention to the fact that some of the games that exist in the market nowadays can be harmful to the child physically, religiously and intellectually.
So, the guardians of the child should make sure that the things he plays with do not cause him any harm.
2- Breast-feeding the baby is obligatory as long as it can not do without it. The scholars are not agreed over this issue. In the Malikite school of Fiqh, scholars believe that it is mandatory on the mother to breast-feed her baby as long as she is the wife of the father of the child. But if she was divorced a Bain divorce (divorced three times) she is not obliged to breast-feed him and also, if she is a noble woman who does not habitually breast-feed her children like women in her status. In both cases the woman is not obliged to breast-feed her child unless he does not accept the breast of other women. The majority of the scholars believe that it is not compulsory on the mother to breast-feed her baby regardless of her being married or divorced except when the baby refuses to suck other woman or the husband can not hire a woman to breast feed his baby. Their evidence is the following verse: Allah Says (interpretation of meaning): "But if you make difficulties for one another, then some other woman may give suck for him (the father of the child)."[65:6] And this verse Allah Says (interpretation of meaning): "The mothers shall give suck to their children"[2:233]
The scholars claim that the meaning here does not reach obligation, it is only likable that the mothers breast-feed their babies because their milk is more suitable and they feel more compassion and love towards their own babies than other women. From this, we conclude that the suckling of the baby is an obligation on his father just like all his other expenditures.
Allah knows best.