The good thing about going to COE is, the drumbrake issue is already known to be widespread so they won't need to test your car, they will just replace it.

Bad news is, I have replaced my drumbrakes THRICE (twice at COE), and the sound is still there. So my advise is, until Proton issue an official recall, there is no point coming all the way to COE if you are far away, unless you fancy a new pair of drumbrakes which will make sound again in a month or so.

AFAIK, only FLX and FLX SE.

Bootlid?
No. Install aftermarket around RM100, autolock when brake is pressed.

Up to you. I shift to N if I know it will take more than minute. Else I just keep my feet on the breakes.

Shifting to N also have the benefit of allowing the clutch to cool, but in normal daily driving the benefits is negligible.
IMO, didn't need it in the first place. I'm actually fine that they left it out, serves nothing more than aesthetics IMHO.
SOS