Whether or not coconut flour can be substituted with all-purpose flour depends on the recipe in question. Coconut flour does not have the protein called gluten that is in all-purpose flour, so their baking characteristics are quite different.
No - the reason why all purpose flour is used, is that it has gluten in it that forms pockets that trap expanding air from the raising agents - almonds are not glutenous and will not rise. The best is to substitute half almond meal and use a gluten free flour instead, that is specifically manufactured for whatever it is your cooking or baking. It all depends on what you're making.
Yes, but make sure you measure and substitute by volume and not weight. Use measuring cups.
Sapin Sapin is a glutinous rice and coconut dessert, traditionally calling for rice flour. If your recipe calls for all-purpose flour, you can safely substitute equal parts brown or white rice flour.
Self-rising Flour
yes enriched flour can be substituted for all purpose flour in a cake
yes
In general, yes.
All-purpose flour can be used as a substitute for cornstarch.
yes. They are the same thing. Plain flour is an Australian term where all-purpose is the American.
yes
yes
yes you can adjust the water
Yes :)
Generally you can, yes.