This is based on my experience and the JP wiki, so this information may not be entirely accurate.

Award 12: Characters obtained as advanced-class units may have to level reset to count.
Award 14: Includes the Mandra Prince and Princess bosses. Sealing enemies does not count as defeating.
Award 16: The max Client Level is 15.
Award 19: This includes unique skills, so you need everyone at least at level 10. Also counts skills you had before Level Resets. Skills shared between different classes only need to be learned on one of them.
Award 20: Have Konomi use a Fish Sausage in battle when she has her unique skill.
Award 23: There are 108 sub-events in the game. You need most of them.
Award 25: Sealing does not count as defeating.
Award 33: There are 168 seal-able monsters in the game making for quite a bit of leeway. However, you still need to seal all monsters to get the true ending.
Award 44: Everyone must be level 99 at the same time; it doesn't count it if they were 99 and you reset.
Award 48: It means it when it says almost. I got it when I was around floor 28 of the tower, and hadn't even touched Dark Cathedral



I've put together another guide for knocking out the sub-events https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3188812234
It's mainly based on this JP list: https://w.atwiki.jp/th2dt/pages/124.html

You can skip 8 of them.