Honking/harmonica noise when in reverse

I have a 2008 Honda Accord LX with about 25k miles on it. I took it to a Honda dealership a few weeks ago for an oil change. I was advised that I needed to rotate my tires (which I knew but hadn’t done) and also that I only had “1 day of driving” left on my brakes. The following occurred…

*Noisy brakes began + a little shimmying when applying the brakes.

*Noise even when not applying the brakes.

*Honking/harmonica sound when backing up and NOT applying the brakes.

Is the backing up noise a brake problem or something else?

Would love some advice from the experts that don’t stand to make a buck off of me!