There is no online sandbox. The camera API complies with the OSC API from Google.
https://developers.google.com/streetview/open-spherical-camera/reference
You may be able to build your own tests using the OSC specification and the THETA API.
https://api.ricoh/docs/theta-web-api-v2.1/
If you want to test sample media, there is some here:
Sample Media and Development Resources
and specific to the SC2.
https://theta360.guide/special/sc2/