I tried to put different shapes on a curve path and had success with circles/ovals and stars/polygons.

BUT not with rectangles , even after I convert it to pattern, it just shown a mess.

My ultimate goal is to put footprints along the path, but more strange things happened. Anyone can give me direction?

Try adding more nodes to the rectangle. There's a function to do this quickly and easily, but I can't remember exactly where

Are you copying the square and then applying it to the path? If I take and copy the path and apply to the square I get a mess, but if I copy the square and apply to the path I get a path that resembles a winding roadway.