A: Probably not. If the sofa doesn’t slide around on a wood floor, it probably won’t slide around in a riser pocket.
The image below shows a bed leg the is inside a riser pocket. This riser pocket is larger than the shown bed leg, but the bed does not slide. At Furniture Risers, we sell Non-Skid Strips (see attached image). The strips are not usually needed, but are helpful in some slippery situations and can be applied inside the pocket and/or to the bottom of the risers on the hard floor.