No, you just pay once for the licence, if you don't plan to sell your games, you can choose the noncommercial version. You just enter the key that you receive after having purchased it and can use the AM that you have already installed on your pc as full version then.
Not sure because of the screenshots. You should be able to see the "Add an Attachment" area under your post window when you post a reply. With help of the buttons you can browse and upload a screenshot from your pc. If you had difficulties uploading, maybe the file size was too big? How big was it and in what file format?
You need a homepage or a free host where you can upload your game. Here is a list of free hosts:
http://www.adventuremaker.com/phpBB2/vi ... php?t=1302