Yes, I have a list of about 15 different worlds. I don't know the maximum.
Yes, you can create as many worlds as you want.
Move the world into the memory stick in .minecraft
Minecraft is really good. There are lots of users playing it and you can also join other peoples games and create buildings or even destroy their buildings on their saved world.
If I understand you right, you can access any amount of accounts on one computer, it's just all the world saves will be in the same file for all the accounts. If you saved all the worlds on that computer all the accounts will have access to all the worlds in there.If you have two computers with a new world saved on each one then you will not have access to each others world. If you accessed one account from a strange computer then you won't be able to access your world saves from your other computer.The worlds are saved to your computer, not the minecraft servers. You can still start another world but then when you get back to your other computer you won't be able to access that world.
In the free version, worlds cannot be saved. This is meant to urge you to buy the actual game. In the full version, when you exit a world, it will autosave, like in all other editions of Minecraft.
alot
Find the world in your 'saves' folder (which is in your minecraft folder) and copy it to another location, like Documents or Desktop.
If you are playing online, it will save the world saves to your hardrive, and if you are playing on the downloaded version, it would depend on where you saved the file. If you saved it to the hardrive (which is default) it will save the world files to the hardrive, obviously. If you saved it to a flash drive or removable storage, it will save the world files to that instead.
You may have corrupted the world by using mods or other unlisenced programs to edit the game. It is best to revert to a backup that you have saved before.
Yes. Each world in Minecraft is saved as a separate file. If you open the start menu and search ".minecraft/saves" (without the " signs) you should be brought to a folder containing all your different world saves. They will be named whatever you named them in the first place, eg. JoeBlogs world. Simply copy the world folder you want to the .minecraft/saves folder on the computer you want to play on.
A world seed for Minecraft 1.3.2 like that is: Artomix.
Yes you can but you can only have one per world.
anywhere besides up or down. :)