1. Is it possible for someone to learn how to program a game with SmileBASIC, or do they have to know how code works before they start?
2. How many pixels can a game be?
If you want to publish an eshop game or a computer game, or whatever, then other experience is required to start doing that. But SmileBASIC is independent on it's own and is a comparatively simple language to learn the basics.
As for screen size, the top is 400x240 pixels, and the bottom is 320x240 (though don't quote me on the bottom).