Does the game loop? How do you mean?
I PM'ed you the answer to your first question - I believe there are 10 levels counting by how many bosses there are.
Loop... in shooter parlance, this is when the game doesn't end after you defeat the final boss and allows you to continue playing the game -- from the beginning. Usually the second loop (and third and fourth) increase in difficulty (i.e. bullets speeded up, different enemy formation, new boss patterns, etc.). Your score isn't reset either, so you get to go for that "high score".