Quick answers
Three decisions that unblock the opening.
Is there an in-game map?
No conventional map. Use monuments, the coast and major structures as landmarks, or follow the next-milestone guide when lost.
Does resting save my progress?
Save and Rest are separate choices at Crystal Monuments. Save deliberately after an important pickup.
What opens new gaps?
Holy Sword Endu gives you Wind Dash; later upgrades extend the places you can reach.