This tool seems to have been renamed or changed in 4.3, but this is my first time in the Sculpt mode and I'm having trouble finding out what the equivalent is. I'm sure it's trivial for those with some Sculpt experience.
Hi there, I'm trying to complete this exercise but I checked and my now doesn't get anywhere close as sharp as it should be. I think the settings of the brush have change a little bit. Is there away I can sharpen those edges to the max with that brush? 
Also I noticed I deform the Ring, is there a way I can get the original shape by removing the sculpting?

If you sculpted the shape and ran out of undo's, best thing to do is either start over and sculpt again or simplify the shape with the smooth brush. Kent always pinches the corners with the pinch brush to get a sharper edge. You see him doing it and you think ah perfect, looks easy, then you go and try it and you end up with a mushy mess. So it takes practice.