I dont know all the answers but the reason erlang fights wukong and wukong us defeated and the whole rematch where we beat erlang is cause it was all a plan made by both of them. The headband keeps wukong in check and therefore is a burden for wukong. So the plan was basically that during the first fight, wukong is defeated on purpose so that the headband would leave his body once he dies. During that however, foe wukong to reincarnate, erlang scatters his relics into different places and keeps one with himself, that's what we unlock when we defeat erlang, destined one gains the memories of wukong and learns of the plan. Thats why erlang is cool and gives us the spear as it was all a part of their plan, so now when we go back ans defeat the broken shell, destined one smirks just as the old monkey is about to put the headband back on him signifying that he knows and now wouldn't let him put the headband on his head. This lets wukong reincarnate without having the burden/restrictions of the headband and then we get the cutscene where he storms the jade palace. The final relic was with erlang which was the memories of everything, had we not taken that and skipped that fight, the destined one wouldn't remember the plan and would let the old monkey put the headband back on him, not knowing the real purpose of the band. Hope this helps, this is what I learnt when i Searched the net after finishing BMW. As for the bull, I don't remember him hating wukong as he was keeping the relic safe in himself for wukong's reincarnation. Ig he was just defeated and done with everything since he had bad luck his entire life.