How is the commandment ''all animals are equal'' not upheld in the farm -- especially with the pigs.
You can see that the pigs are being treated differently from the other animals just about as soon as the revolution is over. Already in Chapter 3, the pigs are clearly treated better than any of the other animals.
Let me give a couple of examples. First, the pigs do not really do any of the actual physical work on the farm. They are always supervising the other animals rather than actually doing anything that is physically difficult. Second, even though they are not exerting themselves, they get the best of the food. They are the only ones who get any of the milk or any of the apples.
Things only get worse from there, but you can see the trend starting already in Chapter 3.
The answer above is exactly right. I would only add that it's not so much that the pigs are being treated differently as that they're simply acting as if they have the right to better homes and food and education and everything else than any of the other animals on the farm. The other animals are simply not bright enough or assertive enough or even aware enough to stop the pigs from their rise to privileged position. They're used to obeying, something the pigs use against them time after time in Orwell's Animal Farm.