I’ve brewed beer with an instapot before (all grain, turned out acceptable), but this sounds like the worst way for someone to try to get into making wine. Starting with cheap grape juice, using bleach to sanitize, and a 48 hour cook time? I’m guessing you need to concentrate the sugars to get the right ABV, but that seems like a lot of work. It’d be better to sanitize by using the pressure cooker function, it’s not high enough psi to kill everything but should be good for most things. If you’re going to tell them to get a specialty yeast, why not tell them to just buy a small batch?
Sounds like prison hooch.