I'm a lazy person and couldn't be bothered to translate it to MC forum's markup. So go have a read and feel free to comment here.
Minecraft Alpha c0.30_01c to 1.12..X convertion guide *here.
P.S. Pleases feel free to correct my formatting, spelling & grammar as I am dyslexic and so am bad at these things.
> [Info]: incoming transmission
> [Info]: timestamp 140120181444
> [Info]: end transmission