re: 1. Gizmo greyed out. as pictured in your example... Once u choose an axis ( highlighted in yellow in your example ) You can now rotate from "anywhere" in the viewport ( if rotating by positioning on the reference grey part is absolutely necessary fer some reason ) with the middle mouse button pressed instead of the…
2/3: I'm with Bartalon on that one. 5: This is the result of namespaces, it's under the import options, and controls for for your scene are in Window>General>Namespace Editor. It's in place to keep naming local for each object, since Maya can only have one name for anything in a scene. A scene with multiple characters that…