Hey Nedko,
Glad to hear from you.
Your questions are very logical. But before I answer them, I would ask you to watch that video:
After that, if you still can not understand it, ask me again, and I will answer. It is not that I don’t want to write the answers, but I believe that by watching the video, you will understand even better how the Walk Forward works. Because it is visual, this is why I do inline courses, which is the easiest way to learn it all.
Please, watch it, and let me know if something left unclear.