There really isn't a limit on the resolution, but I'd suggest never to exceed 1024x768. Well, the commonly submitted (not accepted) size is the default size (550x400), but don't let that stop you if you need a bigger res than that. They won't reject your movie unless you exaggerated on the size.
Can't say there's really a way to stop it from looping, unless it's embedded to an HTML page. If it's the case, you can disable the loop via Publish > Publish Settings > HTML, but it being disabled only works when you preview it in HTML.
Of course, you can always add "stop()" to the last keyframe, but if you don't want to be bothered by moving around that keyframe whenever your animation gets longer, just paste this code on the first keyframe of your movie then leave it alone.
this.onEnterFrame = function(){
if (_currentframe == _totalframes){
stop();
}
}
As you can see, it'll stop the movie when it's on its last keyframe.
Anyways, you're doing a great job at learning! :) I really hope there will be more people like you who would actually be willing to go and try to research for answers himself, instead of just noobs asking "give me code to do X". Keep up the good work.
