Multiple Minecraft Problems?

Multiple Minecraft Problems?

Added (1). I played Minecraft on a friend's account for years before I recently finally bought the game for myself. It was fine for about the first week then it stopped letting me use commands. As in I type / and it does nothing. I even reset the command key. Still nothing. Now the item bar keeps disappearing along with my cursor. I've logged in and out, quit the game, re installed the game and still nothing. I really wish I hadn't spent the money on the game I loved so much before now. Can anyone help?

Added (2). I've also e-mailed Minecraft support a couple of times with no answer, only to go back to the forum and see that my question had been deleted. This is seriously driving me crazy. All I want to do is play the game I paid for and love.

For the /commands, it will only work if during world generation, cheats have been enabled. If you generated a world without turning on the "Cheats allowed" option, you will not be able to use /commands to spawn in items, etc.

Also for the item bar disappearing, did you accidentally press F1?