DaemonUmbra

On your end, join "localhost" on your friend's end put in your Hamachi IP address

Please read the Logs section of my signature below and provide the appropriate log in the appropriate manner.

Your links are wrong, all of them are the server logs

https://mcforge.readthedocs.io/en/1.13.x/concepts/sides/

Java 11 can't be supported without dropping support for Java 8 due to a library Forge uses, and Java 8 support can't be dropped because it's the version Mojang targets and ships Minecraft with.

Threads merged. No... 1.8.9 is NOT supported, only modern versions are. If you continue to make threads like this I will assign warning points to restrict your account.

Are you planning to just make a thread for every version in sequence until you get to one that doesn't get locked?

1.7.10 is no longer supported on this forum due to its age. Please update to a modern version of Minecraft to receive support.

The filenames of one or more of your mods suggests you got them from a repost site. Please read up on the StopModReposts project (link in my signature) for info on why this is a bad thing.

Try without Optifine

Do you get this issue running OpenJDK?

Modded worlds are almost never portable between versions, as it requires modders to publish their mod in both versions as well as include code to upgrade old save data

You should only use CurseForge. The thing about Minecraft mods is that there's no official modding API so they are interfacing directly with Minecraft code, nothing is guaranteed constant between Minecraft versions, with the possible exception of patch updates(see https://semver.org) which are 95% bugfixes.

Mods can only run on the Minecraft version they were designed to run on, and this particular version of BOP you have is designed for 1.12.2. Since you're new can I ask where you're getting your mods from?

Do you know what Minecraft version that particular version of BiomesOPlenty is designed to run on?

The filenames of one or more of your mods suggests you got them from a repost site. Please read up on the StopModReposts project (link in my signature) for info on why this is a bad thing.

Please read the Logs section of my signature below and provide the appropriate log in the appropriate manner.

Please read the Logs section of my signature below and provide the appropriate log in the appropriate manner.

It's in .minecraft

Looks like mod devs still have issues with indicating their dependencies. Re-read the CurseForge page for Dark Utilities, the dev mentions a mod that it relies on.

How long have you waited after starting the game?

This is intended, not a bug

1.8.9 is no longer supported on this forum due to its age. Please update to a modern version of Minecraft to receive support.

Why do you appear to have a base EntityMoChicken that has not just copypasted vanilla code rather than extending the vanilla chicken, but also the code for every specialized chicken that (at least I would think) should be split into each respective special chicken?