Covered by the Buddha in MN 109 and other places which I do not remember right now (remember that all these questions have all been asked at the time of the Buddha and were answered by Gotama himself - that is where sutta study is helpful & important).
Mostly by putting this kind of questions under the category of "questions that do not help in the process of bringing an end to pain". Brush it aside, when you become an arahant, you won't ask this question anymore.Now at that moment this line of thinking appeared in the awareness of a certain monk: "So — form is not-self, feeling is not-self, perception is not-self, fabrications are not-self, consciousness is not-self. Then what self will be touched by the actions done by what is not-self?"
Then the Blessed One, realizing with his awareness the line of thinking in that monk's awareness, addressed the monks: "It's possible that a senseless person — immersed in ignorance, overcome with craving — might think that he could outsmart the Teacher's message in this way: 'So — form is not-self, feeling is not-self, perception is not-self, fabrications are not-self, consciousness is not-self. Then what self will be touched by the actions done by what is not-self?' Now, monks, haven't I trained you in counter-questioning with regard to this & that topic here & there? What do you think — Is form constant or inconstant?" "Inconstant, lord." "And is that which is inconstant easeful or stressful?" "Stressful, lord." "And is it fitting to regard what is inconstant, stressful, subject to change as: 'This is mine. This is my self. This is what I am'?"
"No, lord."
"... Is feeling constant or inconstant?" "Inconstant, lord."...
"... Is perception constant or inconstant?" "Inconstant, lord."...
"... Are fabrications constant or inconstant?" "Inconstant, lord."...
"What do you think, monks — Is consciousness constant or inconstant?" "Inconstant, lord." "And is that which is inconstant easeful or stressful?" "Stressful, lord." "And is it fitting to regard what is inconstant, stressful, subject to change as: 'This is mine. This is my self. This is what I am'?"
"No, lord."
"Thus, monks, any form whatsoever that is past, future, or present; internal or external; blatant or subtle; common or sublime; far or near: every form is to be seen as it actually is with right discernment as: 'This is not mine. This is not my self. This is not what I am.'
"Any feeling whatsoever...
"Any perception whatsoever...
"Any fabrications whatsoever...
"Any consciousness whatsoever that is past, future, or present; internal or external; blatant or subtle; common or sublime; far or near: every consciousness is to be seen as it actually is with right discernment as: 'This is not mine. This is not my self. This is not what I am.'
"Seeing thus, the instructed disciple of the noble ones grows disenchanted with form, disenchanted with feeling, disenchanted with perception, disenchanted with fabrications, disenchanted with consciousness. Disenchanted, he becomes dispassionate. Through dispassion, he is fully released. With full release, there is the knowledge, 'Fully released.' He discerns that 'Birth is ended, the holy life fulfilled, the task done. There is nothing further for this world.'"