You will need a Studio license for development purposes. The Robot on the development machine will take Studio license because it’s for development purposes.
What do you mean by shared? Same license? Sales team would know this answer for sure.
No, in your scenario, just one license is not enough for development purposes.
Again, what do you mean by this? To have only one Orchestrator for dev/test and production? Technically you can do this but it depends a lot on your environment, on developers permissions etc. And again, sales should know these answers based on the setup you want to have.