Yes it is.
Anything you want.
Almost certainly no.
I don't think you can I'm not sure but I'm pretty sure they would have a download link to an updated INVedit
Invedit. An Inventory editor.
Yes. you can use INVEdit.
You can always use an inventory editor. I use INVedit
Download it from from the Minecraft forum. The link is under "Sources and related links" below this answer.
Try a mod. You could use InvEdit or SPC (Single Player Commands).
It's safe.
if you want items in minecraft the best edit i know is INVedit. download it, open world iventory and edit it. save it to your world next
open up Invedit, select "open from" and chose the world you want to invedit, and search for items you want and drag them into your inventory (the boxes). then click save to world # (whatever you want)