You can't change the seed in the demo you can only in the full edition.
Chat with our AI personalities
No you just log in and play the demo
You can set it in the config file. (server.propeties)
Go to start menu, type in %appdata%, if there is ".minecraft" when you search, then you can. Anyways, why using demo?
Pokemon on Minecraft is a mod, not a seed. Search the Minecraft Forum.
You can play the demo version or Minecraft Classic on the Minecraft website.