The #10 foot is an edge stitching foot. I use the number 5 foot to hem clothes with. The guide on the #10 is much deeper and easier to use to follow an edge IMHO
The sole plate can be tricky and other than pushing down hard in the top right hand corner as you sit in front of it....there is no other way to get it off....but can be hard to move. Putting on another sole plate is putting it on by pushing it down. Sometimes one must push quite hard and you think it won't fit.....but it does.