I was meaning to exclude my first name and just use only the middle and last name.
Answer 1 :
i don't think so because your id wont match and now with TSA new security document requirements
you have make a reservation using your full name including middle name and last name on
the reservation site..
and the ID MUST MATCH EXACTLY if they don't match you don't fly..
Answer 2 :
You definitely will need to enter your last name, you can't book a ticket using only your first name. Whatever name(s) you enter should match the id you will be using when you check in. Middle names are not that important, but if your middle name is on your id and the airline asks for a middle name, use it.