The 'Developer Mode' or 'DevMode' Provider is perfect for experimenting with the Venly API. It also allows you to make fast iterations to your mechanics and/or game logic without needing a dedicated Backend for Server Authoritative calls. This mode is only available inside the Unity Editor, it is not possible to create a runtime build that uses the 'Developer Mode' Backend Provider!
Both Client and Server Authoritative calls can be invoked with this provider. But keep in mind that you'll have to transfer any Server Authoritative call to your Backend for Runtime Builds. Therefore it is advised to group your Server Authoritative calls together during experimentation or development. Once you are ready to switch to a dedicated Backend Solution you can then move these Server Authoritative calls to your Backend.