Mixed instructions from manager

Lately I've been getting mixed instructions from a manager. They tell me one thing and then a few days later or even the same day they tell me something different and then speak to me as if it that way the whole time. While talking to me like I'm an idiot. This has been worse lately. I'm also being told things I should be doing that I was never told I was meant to and there was never any indication. One thing was something that someone else always did or I assumed they were meant to. Because of all this I don't know what they might be saying to managers above them. They are not someone I thought would act in this way, of just trying to cover themselves even if it puts others at risk of getting in trouble. Another co worker has already been doing this and now they are as well. I'm just not sure how to handle it because they are a manager.