Some calipers are "flip flops" which means it will work on either side. The reason for 2 bleeders is because no matter what side the caliper is on the bleeder HAS to point up in order to bleed the brakes. My guess is that is not a Mazda caliper but an aftermarket remake.. could be wrong..
Vented and solid rear brakes have different calipers in the back.
turbo is always vented rear brakes
GXL (lsd cars) I think all have vented rear brakes
S4/S5 calipers are the same as long as u use vented or solid depending on your car/build