What happens with booster 9 and hot staging is one of the most interesting questions about starship at the moment. I can see three possibilities for it - booster 9 gets scrapped without flying and they skip to booster 10, it gets modified for hot staging or it gets launched with minimal modifications. I think modifications before flight are the most likely, but it would be really interesting to see what happens with an unmodified booster. Just how much damage would hot staging do? Pretty much any outcome would be spectacular!