Just now I watch the DVD of the Transformers. But, there's something confusing me:

1) What is the cube aka ALLSPARK actually?
2)Why Megatron dead just right after Sam put the cube at his chest?
3) Why Bumblebee already in the Earth for a long time but the others came just right when the Deception is trying to messed up the world?

Humh... Confuse...