Making a hacked client forge mod

I want to edit/make a mod with killaura or reach disguised in it. like just edit some lines to give me reach. is this possible to with forge and if so is there a tutorial somewhere?
I found somebody who made something like this but it is for 1.7, I want to make it for 1.8.9

You'll need a program called JD-GUI to decompile the mod. Then you will need to learn java to code in reach