Inhalation and exhalation are only changes in breathing depth. Some people will hallucinate and stop eating for a short time. Hunger is good for their health. It is not advisable to go on a hunger strike like crossing the valley.
There are many understandings of immortals. The immortals in the popular concept don't exist in reality, so they can't become immortals by any means.
It is no problem to take breathing and breathing as a way to keep fit. Don't indulge in it, and don't fantasize about practicing any special functions.