No, it still feels like you were only asleep for a little bit. The reason for this is because when you have a lucid dream (or any dream for that matter) it's not until the end of your sleep schedule, during REM sleep. Plus you typically run through several dreams in one night.
No. Lucid dreams happen during REM sleep. Your body enters a kind of paralysis during REM sleep as self preservation, so you don't physically act out your dream.
In a normal dream, it's more than likely you'd forget being in presence with a mirror; like I said, your image will appear blurry or not at all. In a lucid dream, results may or even will be scary, and can lead to lucid nightmares. (which are anyway easy to wear off.)
In a lucid dream a mirror will most likely show you your body disfigured, which could lead to a nightmare. (although nightmares with luidity is easy to fight off.)