Boxer is strong.
He hit a guy in the head and knocked him out in one hit
"Napoleon is always right" This means he fully thinks Napoleon is the perfect leader for Animal Farm.
Napoleon was a power-hungry guy who wanted nothing but to control the farm and he was allowed to because by the time he started abusing his powers everybody assumed he was always right and that he was the best leader for the animals.
The rebellions important because the animals got free from Mr.Jones and fought the humans.
The Windmill symbolizes the celebration of the animals being free and being their own civilization because it was built using stone by all the animals.