where could I find the manual for v4?
There currently isn’t a complete manual for V4 or V5. There is a “work in progress” manual at http://sambapos.com/wiki but the information on the forum is far more than documented there. I would suggest if you need something, just search the forum, or take a look at the tutorials category.
As a good starting point, there are many links to some relevant topics about getting started in this post: