How can you tell if you've past stage one of the sleep cycle? Do you not feel well rested in the morning if you didn't?

Sleep Staging. Is done through recordings in a sleep lab by using measurements of the electrical activity in your brain/muscles while you sleep. You will always go through stage 1-2 which are light sleep, rem which is dream sleep, and at your age also stage 3 which is deep sleep. If you don't feel rested despite sleeping 8 hours you should speak to your doctor, who will ask evaluate you for a disorder.