For the backwards bit, add this to the button actions:
on(press){
_root.GOBACK(this);
}
on the main timeline, add this function:
function GOBACK(mc){
mc.cnt=0;
mc.onEnterFrame=function(){
if(this.cnt<7){this.prevFrame();}
this.cnt++;
}
}
For the going forwards bit, add this to the button actions:
on(press){
play();
}
Then add this to a frame in the MC, 6 frames on from where the button is:
gotoAndPlay(_currentframe-12);