Copper cogs will allow you to rotate objects like pistons and dispencers. but they can oxidize, when they're moving they oxidize faster, waxing it will work but it will wear off when the co is moving. oxidization will slow down the gears and when it fully oxidizes, it won't be able to move until you remove the rust.
yes, this update is going to bring back copper golems, and this will add more uses for them.
if you right click the golem with a button varient, it will only press that specific button varient, if a copper golem has a oak button in it, it will only press oak buttons