Can prepasted wallpaper borders be put over painted walls

Absolutely!

Yes, the prepasted borders are especially easy. Just be sure to have a dry cloth to catch any drips as you install.

Yes. I've always used vinegar & water; pour in a plastic pan, & with a dish rag, just go over the area, like you're washing the wall down.

Yes. If it is put over unpainted walls, it will be terrible (pulling off drywall) when you want to remove it or change it out. It comes off moderately easily when it is over painted walls. (You have to score it with a "frog", wipe a solution on it and let it soak for 10 minutes, then pull it off, and repeat to get the remaining paper off.)

I have done it often but the last couple of times I did I could not get it down when I wanted to repaint my walls. I tried every remedy i could find on line. I had to find border that would fit over what I had and what I liked. Not an easy task. I even had professional painters say they could get it off, well they could not.