Almichaud,
That’s because the single layer is a background. Backgrounds have limited functionality (to protect them, I think…)
You can convert the background to a layer by double-clicking on it in the Layers palette. Then the items you mention would no longer be greyed-out.
I would recommend, however, that you leave your background intact and, instead, work on a copy of it as a layer.
You can do this via the menu (Layer -> Duplicate Layer), or the Layers palette (click-drag the background to the "new layer" icon at the bottom of the palette… the center one that looks like a small square with one corner turned up), or, also in the Layers palette, right-click on the background and choose Duplicate Layer from the context menu (don’t fiddle with the Destinaton portion of the dialog).
HTH,
Byron