A:AnswerSort of... The faceplate does sit inside the grooves of the outer shell; however I think it's the fact that the faceplate is sticky on the inside (facing the screen) which keeps it in place. There are specific directions on how to put it on... I HIGHLY recommend following them.. since the phone is sensitive to touch if you develop an air bubble you will loose that touch sensitivity.
A:AnswerMy phone snapped right in without any effort and volume buttons work fine. Also mine came with rubber rim installed already so it makes me think you got a previously used or certainly damaged case.
Mine functions great on the 5S!