1. Afaik, the filesystem is an abstraction that makes it easier to work with files on local and remote systems and it leverages blocks behind the scenes, but the main reason seems to be simplifying the usage of various filesystems. In fact, if you look at blocks, you can create a block for a filesystem - img 1
2. The UI is a good place to see that - img 2
3. For dev vs prod I recommend using different Orion instances and switching between those using profiles - this way, there's no need to hardcode any environment information