What changes have been made to the weekly meetings over the last year of Animal Farm?

At first, the meetings are secret.  But then the
revolution happens and they don't have to be held in secret
anymore.

After the revolution, the meetings happen every
Sunday.  At the meetings, any animal can put forward a proposal and they all vote on the
proposals.

Eventually, by Chapter 5, only the pigs put
forward any proposals.  But all the animals still approve or disapprove of these by a
majority vote.  By the end of Chapter 5, though, Snowball has been driven off the farm
and Napoleon has announced that there will be no more regularly scheduled Sunday
meetings.