Since nobody create this, i think is ok to make 1 to ask.

If i would like to resign, my resignation letter should be addressed to my supervisor, my GM or directly to HR?

If I need to serve for 3 months notice as stated in my employment agreement, then do I need to write in the letter that I will worked until what date?
If need to write the date, then how about if I or my new employer like to pay for the remaining 2 months notice, then should I stated in my letter as well so that the leaving date will be adjusted?