I noticed most of your questions have to do with things I know about so here is another answer for you.
Astral projection comes from spiritualism, the belief in sort of a spirit body or a “double” of the physical body. Spiritualists believed this astral body could be separated from the physical body, and when it did so was composed of a spirit and mind and body. (3 things)
Actually, true exteriorization is the spirit itself leaving the rest behind and being completely free, able to do things without a body.
Meditation is an attempt to do the latter. The original Buddha apparently was able to accomplish this but it took him many lifetimes until he realized there had to be a better way to improve mankind so everyone can do what he did.
Unfortunately today, true Buddhism is altered and we are in worse shape as humans so it is difficult to do without learning again what we forgot.
Some people take drugs to achieve temporary release – they might call it astral projection, or whatever they think it is. But it is a terrible trap that will prevent real exteriorization
If you want astral projection, you might be able to mock it up by meditating. If you want true spiritual freedom, well that is a whole other ball game.