Outaway Cave's alternate routes in the new Snap number just two, making the total number of routes through the location three. Here's how to unlock the two alternate paths.
Outaway Cave Alternate Routes in Pokemon Snap: Rimstone Path
The first alternate path for Outaway Cave is called the Rimstone Path. Once you've reached Research Level 3 you can tread this new path. To get on it, you'll need to wake up the sleeping Crobat to your left when you're on the normal path. Once it's awake, lure Gengar out of the upside down portal through Melody and behind a sleeping Crobat. If you do this, the Crobat won't appear later on to upset the Rampardos, opening the alternate path.
Outaway Cave Alternate Routes in Pokemon Snap: Underground Flowers
The second alternate path, known as the Underground Flowers path, can be accessed in the Crystal area. By using Illumina Orbs on Mawile and Carbink, you'll be able to make Diancie appear. That will in turn calm another Mawile and reveal a path to go around the underground cave in a new direction.