there will be no chlorine in your cycling tank, it disappears after 24 hours, like magic. however, fresh tap water contains it, hence the requirement to use dechlorinator.
You dont HAVE to use dechlorinator, it simply depends how much chlorine your water board put in the water. i very often do a 20% water change and dont bother with dechlorinator and i even half dose when i do a 50% change. Purely because my water is pretty chlorine free. It pays to be safe, and just do what it says on the bottle, until you are klever enuf around fish and keeping fish, innit. brap.