Are there missables?

In order to get platinum, you need to play twice. That said, the technically missable things are as follows:

  • It is technically possible to get your motivation locked into place at a low level without a way to raise it. The simple way to avoid this is to not goof off too much between the time the plot automatically maxes your motivation and Chapter 10. Motivation affects endings so you want it high.
  • Raoul will give you a choice as part of his events. If you pick the wrong one, you don't get a trophy.
  • A boss will ambush you in Chapter 10. Defeating it is not required, but you are unlikely to beat it without preparation and you only get one chance per run.

What do I need to do to get all achievements?

For the most part, beat the boss listed above, beat the game with both protagonists, get all ends, see all events (they aren't missable except Raoul's choice). You'll also grind both levels to 99.

For the 'hidden' ending requirements, make the Flying Board for Lotte, and do 100 non-main life tasks for Stera. Keep motivation high. And, in Plus/DX, view all the events about the seeds.

[PC] Why does the game run like garbage?

Plug in a controller. Yes, really.

Alternatively, if you are on laptop, you need to make sure the game is not running on integrated graphics.

Windows 10 Settings -> Search "Graphics settings" -> Browse -> Select the game exe -> Options -> High Performance -> Save

What is the difference between PS3 and Plus/DX?

Quite a lot of new story content, DLC included as part of the package, and Ayesha and Logy as well.

What is the difference between Plus and DX?

DX runs a heck of a lot better. And a speedup function.