From my limited knowledge and from reading the article, the patient didn’t play the saxophone the whole time, just during integral times.

Similar success without it - maybe but the brain is quite complex and no two brains are the same. Without the patient being awake and playing the sax, thereby activating those neural pathways to check if they are working properly, likely less of a probably of the same success. This helps the surgery team map which nerves are critical.

In the article it says that playing the sax is important to the patient and they wanted to make sure that the patient would still be able to play after the surgery. It’s important that not only surgery is successful but that the patient has a good quality of life. It doesn’t necessarily have to be playing the sax but could be any number of things that would be important to the patient - singing, playing the piano, dexterity in hand movement, etc.

Bathroom - they usually place a catheter so the patient wouldn’t feel the need to #1. Usually before any planned surgery, it’s required to not eat 24 hours before so #2 is unlikely. For craniotomies, usually you can eat a light snack if it’s before midnight.