You have to create a whole new account and set that to the free month. Once the month is up you can then upgrade to account to a gold account (pay monthly, every six months, or yearly)
yes 3 months actually
No 1 month.
if you are new and have never created a xbox live account you can create up to 3 free accounts per xbox for free and yes they are a 1 month
To buy with a credit card is £5.99. but if you are using gold 12 month card its 40 pounds a month