I have been meaning to experiment but haven't gotten around to it yet.. Will certainly update once I do so :) --DK
From what I have read (but not used personally until now), you can replace wheat flour 1:1 ratio with quinoa flour. Since this is not yeast based, it should work I think. --DK
Usually old stock of baking powder could be the reason. Another possibility is that you might be overbeating the batter. Just fold in the batter - it helps to incorporate more air into the batter and will help it to fluff better while baking. Hope this helps --DK
By mushy do you mean Raw? cos if its uncooked then its mostly the oven that's at fault. If its uncooked then here are the possible issues : 1) Oven temperature is too hot making the outside cook faster than inside. 2) Too much batter in cup can cause uneven cooking 3) Oven rack not centered in oven. This particular muffin is meant to be moist as mentioned (but not mushy). Try baking non fruit based muffins to verify if only the fruit based ones are what that comes out "mushy" for you
The sour cream would make this only richer and that sure is not the problem. You need bananas just enough to give the cup measurement I mention. Did you have any reason to use more? I think that might have been the problem. As for it sticking to the liner, grease it lightly before dropping the batter into it. That helps with the sticking issue.
Measurement is the same. It will taste a little different from what I made, thats all :)
Maida is always referred to as either "maida" or "all purpose flour". So here I mean THE wheat flour. Though Olive oil can be used in baking, it depends more on the kind of recipe for using Olive oil. Will it alter the taste, texture and the like. But yes, olive oil will alter the taste as against vegetable oil.
Well, There is no substitute for Quinoa. Simply refer to other recipes that do not use Quinoa. Hopefully you get this wonderful ingredient soon!