You need to turn every switch once (to the left), but the switch in the flame riddle room has to be set back (after obtaining the chest). In the top right are 3 switches close to each other. The lowest of those three also needs to be turned back after the other two are active.
Viewing post in help i need help with one of the puzzles
The king of Amagal can be found during some event. I think it was part of Chiyo's event but I can't clearly remember atm. ^^"
No, you can't dodge the boulders in the dungeon where you find Sandra. There isn't anything past them,. There also isn't anything past the bridge where the soldier is blocking the path (yet).