1) Hmm, you don't want any buttons to work at all or just any other buttons to work when you press down ?
I'll guess it's the latter one.. Make an boolean and set it to false. And add another condition to the other arrows (Not down) If boolean = false
And then in the down arrow pressed set boolean to true. In that way as soon as you press down the other ones don't work..
Hope you get it..
2) There's an example of this in the included examples of C2, parallax.. It's basically putting background on another layer..
Cheers !!