Where is the hidden post game dungeon located

I've looked everywhere with the airship and just can't figure out where it is located

Is it even possible to get every Rogress in Arc Rise Fantasia in one playthrough?

Or does Alf's party automatically get the ones you decide to get at a later point......

If so do you obtain them at some point later in the game

It's found just outside of an inn located on a small island covered with trees that have colorful autumn leaves

You can't get all of them initially however after a certain event you will get all of alf's rogress'

Where are the locations of the post game bosses?

Where can I find the optional Rogress that aren't required to progress the story?