You can destroy something without taking it out of orbit. The pieces will happily carry on along their orbital trajectories.
It's easier to put something in orbit than to hit something in orbit.
Well I'll disagree with my own unsubstantiated claim. Consider that its easier to manufacture flak shells than make airplanes. The same applies to space.
Not meaningfully. If you can get into a similar orbit, it's easy in comparison to intercept.