I have the XYZ of the Far Lands , but my dual-core crashes there. I have the latest non-snapshot version (1.7.10) , but my dual-core crashes when I get there. Also , can the Far Lands be reached on superflat and in the End/Nether?
The Far Lands have not been in the game since Beta 1.8. The current world size is technically infinite, but according to the wiki, the player cannot walk past 30,000,000 in any direction. If you are playing in a current version of Minecraft and you teleport yourself further than that, I wouldn't be surprised if your game crashes. If you're not teleporting that far, I'm not sure why your game would crash.
In pre-Beta 1.8, the far lands occur in the Nether. The end simply has no land much past the main island so there would be no weird terrain generation that far out. The superflat world type was not added till version 1.1 of Minecraft, so there is no way to have the far lands there.