How to make the Skin work for old Minecraft Versions without Mods on MultiMC

First you need MultiMC that is basically the best Launcher for playing the old versions of Minecraft.

Once you have create your Instance you have to edit it by clicking Edit Instance in the right panel

Then you have to go on Settings, click on Java arguments in order to activate it, and then paste the follow command line:

-Dhttp.proxyHost=betacraft.uk -Dhttp.proxyPort=11707

Now just press Launch and you're good to go!