medication labeling

Hi all, I'm new to the website and new to nursing. I will be graduating from an accelerated program at the end of March and I had a few questions.

1) the policies and procedures that I have been taught at my future hospital require that all medication is labeled before you leave the med room and bring it to a patient. However, I have noticed that, in the ER and other busy places, some people ignore this policy when they are just administering a few simple medications. What is the common practice for labeling medications (IV bags, syringes, etc.)?
2) Another policy at my hospital is that the US tech will perform all ordered ultrasounds. However, again in the ER, nurses or doctors often perform a bedside US before an order can be officially written. Is an ultrasound within our scope and practice or is this one of those grey areas?
3) Another policy which I have read about in text books and at my hospital is that anyone receiving IV medication must stay on the unit for at least 15 minutes before they can be discharged, however I have witnessed patients discharged 5-10 minutes after receiving their medications. What is the common practice in this case? Does it depend on the type of medication?
-I would appreciate as many points of view as possible.
Thanks for help,

Rob