My fuel door says it also however I suppose it also depends on what is classified as "premium" fuel around your neck of the woods.

Manual says 91 octane which is premium for me.

I don't know much about the topic but from my understanding even though the knock sensors are there for a reason and can compensate, wouldn't the engine prefer not to deal with that?

I've used several different cables and have seen no difference between a cheap INPA K+CAN K+DCAN off Amazon and something more expensive.

The FT 232 chipset is the standard