the desert temple Arbiter's Grounds
In the Lakebed temple/ water temple.
Look on the map
Lakebed temple is at the bottom of Lake Hylia. To reach it, you must have the Zora Armor and the Iron Boots. You will know you have reached it when the bottom becomes significantly deeper and you see Zoras swimming about.
his in a room on the ceiling
in the lakebed temple
You can't. You either carry on or reset the whole game.
in the main room
No he is not in the temple but after you beat Lake Bed temple he is in a cut scene after you beat the temple so WATCH CAREFULLY.
After beating lakebed temple, you will have to beat the temple in the desert. Though it isn't the end just yet.
The room with the Deku Toad, the mini boss.
You go to the Lakebed Temple found under(or in) Lake Hylia ;)