So this is gonna be a lengthy one, but try to keep up.
With the release of 1.17 coming and considering that many people(including me) will want to update/port their mods to 1.17, I decided to make this text tutorial.
I'll make sure to cover most of the thing that you may need on your updating process but keep in mind, mistakes can always be made. Therefore you need to follow this tutorial as close as possible.
Keep in mind, updating/porting doesn't require you to re-write your whole mod, however some parts will be changed.