Answer to your first question: Yes, sims can kill other sims. Just use the "Make Food" button, wait until they start using it, then stop the action automatically. I'm not sure if it's the GameCube version, though. I have the game for GameCube and I've tried it, but there was nothing in his/ her hand (because they put it away).
I saw it on another site. Yes, kids can play tag with another child, play in the playground, build a sand castle, etc.
And no, you can interact with ghosts in The Sims 2 and Sims 3, though. Well, in Sims 2 you can play as a ghost without going to a lab and waiting for a phone call.
Here is a video:
[video][/video] http://www.youtube.com/watch?v=MJzSS8GhJ0Q
It tells you how to play as a ghost in the Sims 3.
I'm now in love with the little "despicable" Minions from Despicable Me. I saw the second film a few weeks ago and loved it and now I adore the Minions as well. They're too cute! Who doesn't love Minions? And I might not have a new sig and avy up for a while since I'm saving Images to my 3DS Camera. Look on Examiner.com to read what they're saying in the first film's credits.