I've always been told "best on the back".....you don't want the back breaking free when braking or cornering. That's also why you should never put just two winter tires on a FWD car.
^ This.
...and no, you should never have different branded tires on the same car - most notably, the tread depths should be similar on all 4 tires, but equivalent at least in the pairs (front/back). If the tread pattern is different, and your car has ABS (which it does), then I could see the different tread pattern being problematic even if you don't notice it.