[Poreponko]

a) yes the cube is what created cybertron.

c) Megatron wants the cube so he can turn everything into a transformer that obeys him. (In the cartoon beast machines this is what he does when they return to cybertron)

d) The autobots want to stop megatron from getting the cube because they want to let everyone have a choice as to be "destroyed" or not by megatron and the cube. Optimus wants to keep us alive because we have a potential to do something good or whatever he says in the movie.

e) Not sure as to why everything turns evil in the movie. But i do remember that in Beast Wars, the machines that were created did not have sparks to start out with and they were evil until given a good spark to make them good or whatever.

f) And i think thats why the autobots destroy the cube. But i do know that starscream flies away at the end of the movie and theres supposed to be a sequel,