You get a mod, such a Single Player Commands.
Yes, the mode can be changed.
To smite (kill) another player, you first have to be in melee range of them. Then simply attack them by left clicking until they die.
Unfortunately, you can not change your name on Minecraft!
You can change your minecraft clothes if you change your skin or download a mod.
Texture packs are downloadable files that change the appearance of the game. In minecraft it can change everything from the appearance of the blocks to the mobs and sometimes the default player skin.
TheIronHamster is the greatest player in Minecraft.
To change the gamemode of a player, you would use the command /gamemode and in the player spot you put the name of the person that you want to change the gamemode of
Sadly, you cant change your minecraft e-mail
If you mean Minecraft Classic, this is not possible. Minecraft classic is only meant for building, not survival. If you want to have survival, you'd have to buy the full version. To change day to night in Minecraft premium (full), as of 1.3 the command prompt was added to single-player so issue the command /time set night.
single player mode on minecraft
Look up the default controls on the minecraft wiki page, go to the control settings in minecraft, and change them.