Sorry Pixbae, I only just spotted your question.
Follow Me is one of the basic tools that comes with SU. As I've already said, this tutorial doesn't use any plugins...that's why it's called vanilla flavoured.
This is the problem with Pilou's approach; if you don't even know what Follow Me is, then for the sake of your own learning curve, if nothing else, you shouldn't be going anywhere near Ruby scripts. Learn the basics first. You'll then have a much better understanding of which plugin to use when...and how you can fix it if things go wrong.
The diamond pattern is produced by simply drawing diagonals across all the quads, in a diamond pattern.
Yes...simple maths. The torus had 72 segments, because that was the number of segments on the circle being followed by the template in scene 1. I reduced it to 2 segments...so it's obviously going to take another 35 copies of that double segment to remake the complete circle.