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.