Can the pitcher stand on the mound without the ball pretending to have the ball in an attempt to get a runner out?

No, this situation would result in a balk as the pitcher cannot 'pretend' to pitch in an attempt to deceive a baserunner.

A fielder may hide the ball, like pretend to throw the ball back to the pitcher and then place the ball in his glove, in an attempt to get a runner to step off a base and tag him out ... this has been called the 'hidden ball trick'. But the pitcher may not step on the pitching rubber if the fielder is attempting this. The pitcher steps on the rubber when he is ready to pitch and he can't be ready to pitch if he is not in possession of the ball.

If a baserunner waits until the pitcher is on the pitching rubber to take a lead off, he will never fall prey to the 'hidden ball trick'.