He retained a good chin after that fight. That was a one off. It wasn't like he had no punch resistance after that fight.
No, but it was not the same anymore. His experience started to do things his punch resistance couldn't It was not a bad chin, but it was not great anymore. He would start to go into defensive mode when he was losing, although even against McCrory he went into that mode. He had a long career and fought a lot of guys.