For what recipe? Don't do it unless the recipe calls for it because you could seriously mess up the baking chemistry.
Only use self-rising flour (aka self-raising) as a substitute for regular flour if the recipe gives instructions for doing so. Self-rising flour contains salt and leavening and cannot be used as a direct replacement in all recipes that call for plain flour.Well once I made biscuits with regular flour and they were rock hard, so unless you want rocks instead of fluffy soft biscuits, then you can't use rugular flour instead of self-rising.
No
Yes.
High grade flour or strong flour has a higher content of gluten (a protein formed when flour is moistened) so is mor4e suitable for baking items that require this "strength" such as bread and dense cakes such as dried fruit cakes. A lower gluten content is desirable for more delicate textured items such as soft cakes and pastries.
Not sure what you mean by "high grade flour". You'll get the best results with specified "bread" flour, but "all purpose" flour will work fine, too. Do not use "cake" flour.
Yes they can
No you use special flour from Tibet which is high in the mountains and you have to ride a buffalo there to get it You can use plain flour but then you have to add baking powder, I think you add about 1/2 a tsp.
It is plain flour, but with a medium gluten content.Flour can have a high gluten content - (strong flour) and this sort of flour is best for bread making, or a low gluten content in which case it is best for pastry and cakes (if you add baking powered to low gluten flour - this is sold as self raising flour).A multi purpose flour will have a medium gluten content and thus can be used for both bread and cake baking it is a compromise product.
Add 1 1/4 tsp. baking powder for each cup of flour. Bread flour may not be preferred if making biscuits, cakes, or pastries. Use cake flour or all-purpose flour for those.
flour makes cakes powder made of ceral grains contains high proportion of starches
No. High grade flour is made from a specific type of wheat, usually for read baking but self rising flour is flour with additional ingredients to make it self rising. They are not the same. You can also say that you can substitute the flours but will not get the same results unless you compensate for the differences.