If they did they would be the first ever world champion to switch sports. I think if a fighter did do this Ngannou would be the mostly likely to succeed at it.
Depends. Theres so many belts in boxing so fighters who arent necessarily even that great can sometimes be in the right place at the right time to opportunistically get their hands on one.
If you mean a title of a major boxing federation against a top opponent - I doubt any UFC fighter will be able to. And is very normal being so.
This is very rare that gonna happen. They both are completely different and combat different strategies for almost everything. If it's a similar weight then definitely MMA fighter wins. But if there is some extraordinary boxer who can do this then this gonna be a world record.
If that ever happened it would because the boxing champ was weak and same vice versa. MMA and Boxing require different skill sets. What you would expect of a world champ is that they are the champ because they dedicated their whole life to becoming the best in that sport. If someone could come in from another sport and not trained full time in boxing and beat them, then that says more about the state of boxing then how good the MMA fighter is.
