During a cycle it is good to have some kind of lighting on it. And yes, you can do small water changes during the cycle. Some will say no, you wont get a cycle if you do that, but that's not true. Your bacteria grows in the rocks, not in the water. If you are starting with live rock from an existing system, you will probably not have a cycle to speak of. Possibly a low ammonia level to start if there was any die off from a transfer from one system to yours, but nothing more.