I have a few questions:
1) I saw a video of a guy using sculptris, he was able to rotate the camera by 45°, I have no idea how he did that (he didnt actually rotate the mesh, just the camera). http://www.youtube.com/watch?v=KrViiOLTWTM
Look at 00:51.
I tried every key combinations and google, unable to find out.
2) I don't know if it's a glitch, but it's very annoying: while modeling, I made a selection, used to grab tool to move the selection and then unselect. The problem is that after doing this, it created some displacement at the border of the selected area, and it's impossible to smooth it. It's like I can't smooth at all actually... Any idea?
For the first question, in Sculptris you still only rotate your model (or the camera, depending on how you see it). If you go to options, and click the "Free Camera" toggle, you will be able to rotate your model in the same way. The only way to get specific camera views with Sculptris is by holding the Shift key while rotating your model. It will then snap to the nearest Front, Left, Right, Back, Top, or Bottom view.
For the second question, you may want to use the wireframe to see what's going on in that area. Using the mask also adds in tris to get things as smooth as it can. When you moved it, it may have just stretched some of those areas. Using wireframe you will be able to see what's happening in there. Use your reduce brush in there, combine with a grab click at a zoomed in level to get those tris to a more uniform shape, and you shouldn't have too much of a problem smoothing it again.