It's called Minecraft... creepers have ALWAYS been in Minecraft.
A minecraft creeper is green, tall and always has a sad face. When asked what creepers felt like, Notch said that they were like leaves.
There aren't "ancient creepers" in the application version of Minecraft, there are creepers.
No, Creepers just flee from them.
Yes, creepers were an error, they messed up a pig...
It depends on the mod, but usually he looks like the player character with blank green eyes.
Yes
No hostile mobs (including creepers) are present in peaceful difficulty.
Yes
Yes, they will explode.
Nothing.
They explode once they sees you.