DaemonUmbra

Did you run Java's installer or did you download a JDK zip?

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

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

2.8.2 is a 1.12.2 version of the mod. One of the devs seems to have not cleaned their workspace when switching between MC versions.

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

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

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

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

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

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

Eclipse doesn't list them there until you've used them once already, click the "Run Configurations..." option to see the full list

I would put this down as Twitch screwing up Forge's install process. In the logs section of my signature is a video on how to run a Twitch modpack manually.

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

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

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

It sounds like you removed your standalone Optifine Installation/Profile. You still have a copy of Optifine in your mods folder, this is where Forge gets it from.

Really old Minecraft versions are no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

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

When we say debug.log we're not saying to copypaste from the console window that pops out when you start the game, we're talking about a debug.log file that the game writes in the logs folder.

Any Minecraft mod can be installed by putting it in the mods folder, any mod that requires more than that is sketchy

Locking

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

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

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

Your insistence that your copy of Minecraft is legal has me concerned. Please provide a screenshot of the launcher showing you logged in. As well as the exact way you are running the installer.