: Placing an item frame on a chunk border and breaking it at the exact moment the chunk unloads can sometimes leave a "ghost" item that becomes a real duplicate upon reload.
Because 1.7.10 was the peak of heavy modding, many duplication glitches were actually the result of mod interactions. Mods like IndustrialCraft 2, BuildCraft, and Equivalent Exchange 3 added complex piping and sorting systems that the vanilla server code was never designed to handle.
: Minecraft frequently updates, patching bugs and changing game mechanics. A duplication method that works in one version might not work in another, especially after patches.
: This method exploits how the game saves your player data separately from world data. How it works : Drop the items you want to copy on the ground. Use Save and Quit to Title
Yes, the code still exists. If you download the official 1.7.10.jar and host a LAN world, you can replicate this.