Hush-Hush achievements
Solution not yet known
Skill achievements
Mod Introduction achievements:
Just play any ranked map with mods enabled such as: SOHRNFHD
Yes, NF mod works. You can find SO mod in "Special" category.
Perfectionist (PF) and Finality (SD) achievements must be used without any other mods.
Beatmap pack achievements:
Packlists can be found HERE. You must pass any mapset difficulty for it to count as CLEARED. You can always check your progress by refreshing beatmap packlist.