[Teutonic]

Well, it pretty much depends on the inclination, but I do believe that two clicks is not enough, however depends on the usage as well, some cars are concrete at two clicks, some are barely holding at five....
Since is a new car, you should be ok, but you can check by puting it in Neutral and try two clicks on the same hill, if is moving, then is not enough.
If you don't pull it accordingly it is like you didn't use it.

Anyway, in your case, I don't think you pulled the handbrake enough to lock the car, so it was using the transmission gear to stay in place. When the handbrake is not pulled enough or you release it without puting the foot firmly on the brake first, the clank noise is normal since the gears are the ones that are doing the hardwork keeping the car in place, so they need to work harder to disengage from that tight position.

In the hill, always pull the handbrake until it feels tight enough.