I don't know but I doubt there is a setting on the Instant Pot that's cool enough without the yogurt button. They would all be way too warm and kill the good bacteria that are necessary to ferment it.

I've never used powdered yogurt culture so I can't advise on the amount that would be needed. I would suggest using the amount it suggests on the packet/box. This recipe makes roughly 3 cups or 720 ml. I'd use that amount to calculate it. It is important to get it right amount. Not enough and it won't ferment properly, too much and there won't be enough food for the excess bacteria. Hope that helps!

It does make a difference if you use full fat coconut milk. It doesn't work as well in this recipe.
I'm sorry but I am not familiar with coconut milk in cartons or any of those brands so I have no idea how it will compare and whether it will work in this recipe. Here, full fat and light canned coconut milk is very easy to come by. The only coconut milk we get in cartons is the very diluted kind for drinking that's comparable to soy milk and cashew milk etc.
If your carton coconut milk is the equivalent to what's in our cans then it should be fine to use, but I can't guarantee as the recipe hasn't been tested with it.
I don't have a can of light coconut milk handy to check the fat content but I just checked online and it varies by brand but it roughly between about 15 grams per cup (240 ml) to 21 grams per cup.
It doesn't matter if it has guar gum added or not for this recipe. It was thoroughly tested with coconut milks that contained it and didn't contain it and it was fine with either, hence the reason it's not mentioned in the recipe.
I have no idea if canned coconut milk is sterilized at high temperatures.
Hope that helps!

Any combination of jar sizes that will hold a total of about 600ml (just under 3 cups) is fine. I will say though that the bigger and deeper your jar is, the longer the yogurt will take to ferment and get nice and tangy because the warmth will take longer to permeate through it all and get it going. With smaller jars it will be quicker.

Thank you.

I have only tested this yogurt with cashew nuts. I think it should work if you omit the cashews but the yogurt will probably be runny. Please note that I have not tested it that way though so if you try it you do so at your own risk and I can't guarantee it will work.