The classic Golden Freddy represents Cassidy, who died during the time of FNaF 1, and basically she's part of the Five murdered childrens like in the original, and well, Fredbear had been updated to the classic model which was inactive, (explaining why it didn't attack anyone during the repairs or run away)

After Cassidy's death, Evan awakens again (the crying child), and a relevant detail here is.. Evan isn't just angry at the children who killed and bullied him; he's angry at all humans and finds them despicable because everyone picked on him—teachers, students, EVERYONE.

One detail I find interesting to highlight is the Fredbear-esque design when Evan is in control, and... Golden, or should I say... Yellow Bear, when it's Cassidy

The third one would be in UCN, it would basically be a version fueled by the hatred between the two, Cassidy and Evan together, and then they leave behind only that element of agony and rest in peace, Letting the demons deal with demons (REFERENCE to Old Man Consequences)

So, the third desing never existed; it's a mixture of hatred, pain, and revenge from the two tormented souls.

The will be 'Bear element"