OpenAL is not necessary, MG switched to OpenAL soft.
To run MG DesktopGL you need at least OpenGL 2.0 support and support for framebuffers. Other dependencies are included in the DesktopGL project template (SDL, OpenAL soft).
Yes, MonoKickstart provides a Mono runtime so users don't have to install Mono to run the game. That's all it does, so it's not bound to a specific MG version.
MonoKickstart takes care of this. It provides an executable that will run your game.