*gasp* I'm such an idiot. I apologize. I've mixed up files included in the project vs the files physically inside the folders. I've set everything as it should be now. All of the IDE Project folder files are in the physical folder together as well.
Right now. I'm stuck at extdll.h not being recognized. I've checked the environment variables pointing to the hlsdk multiplayer folder and metamod folder where metamod.h is and added Additional Include Directories in my IDE as following.
But the error still exists.