1) ?
2) Hadlakas Nerois for Yom Kippur, When one sees a tree budding, Lishmoa kol shofar when the second day of Rosh Hashana is on a Sunday and being killed al kiddush Hashem (once in a lifetime).
3) Like mentioned above- this year. The other answer I heard- when Rosh Hashanah begins on a Friday- doesn’t happen in modern times.
4) Vayoshoku Hamayim.