In the files menu, click the name of the file without actually downloading it. That will show you the changelog.
It mentions it uses textures now.
Accessor takes care of shadow, final, and mutable for you. The entire point of Accessor is so you can use a mixin on an interface and cast to it directly. Here's an example.
You're getting an OutOfMemoryError, which means you're running out of memory while loading. Try allocating more in the launcher settings.
Though I'm sure there's an underlying issue there. Does it still crash if you remove liteloader? If so, get support from the pixelmon forums.
There is an example mod in the source repository. You can you that as a base.
The things you need to note is the following. Main mod class needs to be prefixed LiteMod. This class needs to implement LiteMod. There are several interfaces that extent this which represent different hooks in the liteloader package. Lastly, you need a litemod.json which defines some additional metadata.