4 and 5 are the same stretch, changing foot flexion to extension decreases the emphasis on the calf
8 and 9 are both the same stretch at different points both are laying splits (as opposed to standing splits)
10 and 11 are also variations of the same stretch. With the knee down, it tends to...
I think it's really great when people really dedicate themselves to their flexibility, but I would just offer one word of caution: don't go too hard or too fast. Sharp pain in a stretch means you've hit the stretch reflex, which will set you back in your flexibility.
Flexibility is all about...