My daughter is left handed and took to the flute just fine. So there is no disadvantage in being left handed. One or two times should do it if it is just a normal stickiness. If oil or other substance is on it you could try lighter fluid on a Q-tip. If the key itself is sticking in a closed position, or opens slowly when released, the steel pivot of the key would need cleaning and adjustment.
Some advanced flutes have wall thickness options.
Student flutes and most intermediate flutes do not. Neither is better, just personal preference. Just Click here to download a file of staff paper. It is in Adobe Acrobat format.