Imagine a world, where technology allows to summon yourself from the past to your own body.
you can only transfer consciousness from the past and back, no body, no things;
you are not conscious when the past version of yourself is in your body;
technology cannot reach like 5 days into your past, your past version has to be from at least 15 years before your current time;
before the procedure you can choose a time limit, after which the past version would be sent back for you to regain your body;
sending it back to the past creates new timeline, so a "younger you" cannot affect your present in any way.
What would be the reasons to summon the past version of yourself and let it control your body for some time?
You couldn't change anything in YOUR past, because of the different timelines.
My thoughts so far:
ask past version to remind you something that you have forgot (i. e. code from the safe) (of course you would have to write your request in a letter before the transfer, because you will be unconscious until "younger you" leaves);
ask "younger you" to work on something for some time (just so you wouldn't have to work yourself, but have work done), as a reward offering any knowledge of the "future" (because memories are the only thing a "younger you" can take back with him/her to the past) and maybe a few days to look around and explore your present (which is "future" to a younger you).
I feel I am missing something big. Please help!