"Active dry yeast" is not the same as "instant yeast." "Active" (which is actually less alive and active than instant) must be proofed in warm liquid with a little sugar or honey before the mixture is added to your dry ingredients.
Instant yeast is added directly to the dry ingredients and then the liquids, etc. are added later.
The temperature of the liquid for proofing active yeast should be somewhere from 105F to 115F. Any higher can kill the yeast. Since instant yeast gets mixed into all that flour ahead of time, however, the liquids should be 120F to 130F (so they say - I'd never take it as high as 130F, but always use 120F to 125F).
When I was in the States, I had always used active dry yeast, so when that was not to be found here, I had to switch to instant and now I like it better. In fact, I saw one episode of
Good Eats where Alton Brown was not only recommending instant yeast over active, but the package he showed was SAF Instant: the same brand I use here.
Bread flour is bread flour because it has a higher protein content than all-purpose flour (and way more than cake flour). That protein is gluten and it is the network of gluten molecules that provide the "fabric" against which the carbon dioxide released by the yeast can push in order for the dough to rise. Thus, bread flour will more likely produce better results, unless you are using a recipe that specifically calls for all-purpose flour (in which case, the bread flour could be too tough). I'm sure there's leeway to either side of the equation, though, if handled properly.
Edit: HERE is what Alton Brown said.
