diesieben07

This is not ForgeAPI. This is decompiled Mojang code, as such documentation will be lackluster. You need to look at the source code, in particular func_234638_a_.

You need to override getContainerItem.

It uses the server IP I'm guessing.

Then the server doesn't send the hashed seed. You can use the server IP, I guess. ClientPlayerNetworkEvent.LoggedInEvent woudl be a much better choice here. Do not use getPrivateValue. Use findField and store the Field in a static final field.

Threads merged again.

Why did you make a 2nd topic?

The only true way to know is to call BlockState#canHarvestBlock, which requires a player and will check the item the player is currently holding or other arbitrary things about the player (mods may have all kinds of arbitrary requirements for harvesting).

Best way is probably just to delete it and let it regenerate

Your game settings file is corrupted.

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

The docs are outdated. There is only getCapability now, which returns a LazyOptional.

You get the ItemStack as a parameter.

Return an ItemStack that has one more damage.

Look at FishingPredicate.

Its on Optifine to be compatible, there is nothing Forge can do here.