No, you can't cancel 2,1,u+3, but you can cancel b+3,1+2 again. Also, the 2 in 1,1,2 is uncrouchable. Additionally, Quan Chi's skulls don't turn invisible anymore when another skull hits a wall. Actually, I'm not hearing the skulls hit the wall if I fire another one. I think any skulls out disappear when Quan Chi uses a second one, though I don't think that affects the game.