What's going on? New bug?

I have been using Illustrator for many years and I must have turned on/off something, every object, line, text etc. are in highlighted in red line, even when it's not been selected. When selecting an object the red color becomes bolder and can move objects, however, when I use bring to front or send to back it doesn't do anything t

he object remains in the same place, as if it is in outline mode. I've have tried turning on and off the outline mode, preview mode etc. and still doesn't make any difference. Please help me sort out this issue, I have too many designs to make these days. thanks all