The liquid tempera paint is not waterproof because it is a water base paint.
Tempera won't stick to gold leaf. It will crack off as it dries out.
water
Yes
The answer depends on what brand of paint you use. To make sure it is oven safe (this is for any temperature) check the label on your paint to check for any flammable ingredients.
yes
no tempera is a water based washable paint
To make face paint out of tempera paint, you mix flour and water in a small pain on the stove until it is of the right consistency. After you remove the mixture from the heat, separate it into several bowls and add tempera paint to each bowl until you get the shade that you want.
water
tempera paint.
no
you shouldn't eat it obviously since it is plastic, but painting a project that has to be bakes is fine! in fact, if you are painting oven bake clay, the paint will adhere better if you paint before baking rather than after. although you'll want to do a test first in case there's any discoloration or you're using the wrong paint.