I couldn't do crow if I tried really hard. I can't even get my legs up off of the ground. Last time I could do that was in 5th grade.
When I was going to yoga regularly, I occasionally went to a class where we did the headstand against the wall. I think I remember doing it, but I just feel uncomfortable being in that position.
I have to agree with Shootingstar. I feel like those kinds of poses are more advanced. Since I practice at home now, I don't even attempt them.