It should work. I haven't tried requests-cache exactly but in Neptyne you're running with a Jupyter kernel in a Docker container backend, so you do have a filesystem to work with. That file system is mostly ephemeral though -- when you leave and come back, you'll get a new container, so anything you need to persist should live in the spreadsheet itself.

Yes. You can use whatever you want. We do ship with a bunch of useful things installed (requests, pandas, plotly) but you can pip install whatever you want.