Servers are like any Minecraft world, they have infinite terrain and generate more as you explore futher
A world generator allows you to generate random seeds but if you try generating that seed again it will still be the same seed.
They randomly generate throughout the world, to find one just keep digging underground.
There is no ice dimention in Minecraft. Currently there are 3 dimensions: - The Overworld (normal world) - The Nether (hell-like world) - The End (home of the ender dragon)
You have to spawn it in, or re-generate your nether if you have a pre-1.5 map
A Minecraft world seed is what Minecraft uses to generate the terrain to begin with, it does not create any user-created structures like castles, only things like NPC villages, mines and strongholds.
The seeds in minecraft only generate a world's landscape. Whatever you build in that seed is not part of the seed, it's part of your save. You can download other people's worlds though if they have a link
Infinite, as everything in minecraft. However, they are quite rare, and it is easier just to trade for them.
Yes, very normal.
since 1.8, notch has implemented a new terrain generator that simplifies world generation. the world is infinite and dependent on your cpu's capacity to store info & how much of that is deticated to minecraft. essentially, until mc runs out of space, the world is infinite. so are your creations. the sky is the limit my friend.
If you want Nothing AT ALL you can go to more world options and swich it from Normal to Superflat.
currently poket minecraft on the ipod/pad does not support crafting. once updates I guess it will work like normal minecraft were you will have to place a crafting table in the world then click/tocuh it.