Some motherboard manufacturers have bios fules that don't recognize some ganing keyboards. I have a g510 and that happened to me with one motherboard I had. The next bios upgrade fixed it. The Logitech drivers don't loag until Windows loads, but the keyboard should function as a regular keyboard without them.
As for the second problem, I have no clue. I have never had that happen. I rarely use a headset. Have you called logitech support about it? They may be of more help. They were very good with me when I had issues with my G500 mouse.