Does this bottle have an expiration date or does it never expire ?
Yes. We recommend adding ammonia 3 times during the fishless cycling period and a 2 ounce bottle is enough to dose a 100 gallon aquarium 3 times. So plenty to cycle your 36 gallon tank.
Does this solution contain chlorine? The label says it's NH3-N but name is Ammonium chloride.
The product is ammonium chloride dissolved in pure water. It does not have any chlorine in it. The ammonia is measured in units of NH3-N