No, they do it all the time for movies not even out yet. Especially one's like this that will be a much higher demand. link: Netflix: Rent as many movies as you want for only $8.99 a month! Free Trial There is possibly some spoilers in the description about Shockwave, fair warning.
Not odd at all. They will let you put movies on your list even if a release date hasn't been announced. It allows people who might be excited enough by a trailer to rent but not excited enough to see the film in a theater.
Well he is the primary villain of the movie. It is possible that he is above Megatron, or even replaces him as the leader since Megatron has been defeated twice now.