Q: Is it posssible to hide only a step number?
A: It is possible but only not using multistep pages. Here is an example code on how to do it:
This works asuming the background of the page is white (color #FFFFFF).
What you do is temporarely give the stepnumber the same color as the background color of the page and then change it back to the color it supposed to be. You can ofcourse use this to change the color of any given stepnumber or sequence of stepnumbers.