There is only one dialog option with three different answers. Every answer leads to the three endings of the game. other than that just to do the misc achievements like going into settings and so on.
I will explain it in more detail further down in the guide.

Also make sure to increase text speed and such to speed up the game.

There is only only place where you can do something. Every choice here leads to one of the three different endings so make sure to do a single save here. And now everytime you finish the game just load the save and choose the remaining options. Doing all this will unlock 17/20 of the achievements

The remaining achievements are gained from the title screen
as shown in the pictures below press the Gallery button and after that the BGM button when inside the gallery. There is also one for going into config but you should get that when changing your settings

To smoothen out the experience make sure to go into your settings and change the settings to speed up the game. The picture down below shows my settings and which to change.

You also might wanna consider changing the effect setting under system it might make it faster?

I hope you enjoyed the guide. There isn't really a lot to the game but thought I'll just make the guide to clear up that fact and help finish it the best way possible. Other than that have a nice day :)