You must complete the first 4 trials in the opening area - after that you can go directly to Ganon, explore the world, complete one of the 4 main dungeons, do m

You must complete the first 4 trials in the opening area - after that you can go directly to Ganon, explore the world, complete one of the 4 main dungeons, do more temples, or whatever you want in basically whatever order you want. Some things may be easier with prerequisites met but are still 100% possible if they aren't.