You can take anything you want. NyQuil has Alcohol and a mind altering antihistamine in it. Mixing Xanax with any other CNS depressants is dangerous!
You need to ask your doctor about this. Xanax is a downer (anti-anxiety) and Ambien is to help you sleep. You can also ask your pharmacist
Yes you can, cause I take all of those too. :)
Orally, by mouth. It's hits your quicker by doing it thru your nose, but since xanax is not water soluble you don't get the full effects. Don't even try to inject it because you will have no success.