Flours differ widely from country to country, so if the requestor is in US, then it's helpful for the respondents to be talking about US flours. Personally, I would be interested to learn about how you buy flour in US, but in this thread that might be confusing the issue raised in the first post.
Self rising flour isn't a substitute for cake flour. I learned that at age 11 when I bought some and attempted to make a cake with it. Bad decision! Never did that again. Self rising flour is useful for biscuits and that type of product, as it has the leavening and salt already added.
For all purpose flour, I buy King Arthur or Hecker's (a local brand, I think) For ALL my cake baking, I order White Lily AP flour (NOT self-rising) from Tennessee. It's a soft wheat flour from the south, and cakes made with it are just unbelievably tender. I only buy organic whole wheat flour from a local farmer. That's where I also buy corn meal and rye flour.