Can I use Bisquick instead of All Purpose Flour?
You cannot directly use Bisquick in place of AP flour.
According to the company web site and Wikipedia, Bisquick consists of bleached all-purpose flour with several other ingredients, including fat (shortening), leavening (baking powder), sugar, and salt. It is essentially a self-rising flour with added fat. Because of all of the extra ingredients, it will not behave the same as regular all-purpose flour.
Depending on the recipe or application, you may be able to substitute or remove some of the other ingredients to make use of a pre-mixed flour like Bisquick.
Yes, sometimes you can use Bisquik instead of flour. I rarely cook, but I had been ending up with overripe bananas fairly often so I decided to make banana bread. I thought the container in the top shelf of the cupboard was flour. After making four batches of banana bread and one of zucchini bread over a couple of months, the container of flour was almost empty. That's when I found the back of the Bisquik box under the container. I had been using Bisquik all along, thinking it was flour. (I told you I rarely cook! I remember now I bought Bisquik to make pancakes eons ago.) All the bread turned out great. I took it to work, where it quickly disappeared, so that's more than just my opinion. So maybe sometimes you can't just substitute Bisquik for flour, but sometimes a 1:1 substitution works just fine. In fact, I'm a little leery of using real flour next time! :-)