In the quantum mechanical sense, yes things can come into existance out of nothing. They soon however go out of existance. You can see the chaotic undeterministic events when you go into space-time on an incredibly magnified level, e.g. plancks length magnitude. You see that there are rips and chaos even in the apparantly smooth surface of space.
Edge of the universe: the universe can be seen in diffrent ways. You can see it as flat, and no curve. This is infinite and you will never return to a place you just left. There can also be a spherical structure, in which space-time is round and so it is finite, and you will eventually get back to where you started. Etc etc. In basic physics, and as far as humans comprehend, the universe is flat. In the beginning of time, there was no space, so there can be no boundry as space itself was created in the big'un IMO.
