SUBTLETY can be found as the commandments of Animalism are changed to suit the needs of the pigs... most specifically Napoleon. For example "No animal shall drink alcohol" has 'to excess' added after it is assumed Napoleon got drunk and survived.
INCONGRUITY arises as the beginning of the novel's teachings of Animalism include luxuries for everyone and limited work. By the end,
... the luxuries of which Snowball had once taught the animals to dream, the stalls with electric light and hot and cold water and the 3-day work week, were no longer talked about. Napoleon had denounced such ideas as contrary to the spirit of Animalism. The truest happiness, he said, lay in working hard and living frugally.
The above quote likewise demonstrates THE CONTRAST BETWEEN TWO CHARACTERS, Snowball and Napoleon. As a leader, Snowball was inspirational and seemed to believe in the power of the message the Old Major tried to portray. Napoleon on the other hand, as a leader used force through the dogs to achieve his means... which was pleasing himself.
I'll let another editor tackle the passage of time and repetition for you.