All of it, even the switches, is part and parcel to the big picture.
Not really. In some cases it’s okay, passable, in others it’s wildly inaccurate. Remember, real ATC is human to human communication and predictive, human analytics. The sim has a long way to go here (and there are big threads devoted to this subject).
I wouldn’t teach this without first ascertaining whether a person understands the difference between heading, course, and relative position (bearing). Heading is the way the nose is pointed, course is the imaginary line our airplane makes through the sky (or over the ground) due to wind drift, and relative position/bearing is the compass direction to or from another place. Understanding the directional gyro (heading indicator) is the first step in this. Then we can start tying it together. Visual aids and demonstrations help.
You sure can use them in VFR. But remember, VFR is a whole plethora of visual flight rules (all that airspace, weather avoidance, and not hitting other planes or rocks I mentioned above). The word you might use for this is “can I use them in VMC,” which is visual meteorological conditions, meaning a certain amount of visibility and distance from clouds (dependent on airspace, altitude, and sometimes time of day). And the answer again is yes you can. Radio Navigation is one of the three primary methods of navigation I mentioned above in addition to pilotage and ded reckoning.
Think of it this way: if you’re grilling, your neighbors (usually) love to be downwind of you - the way the wind is blowing toward. If you’re going downwind, you’re moving with the wind. Like going downstream. Upwind is into the wind, or like going upstream. Upwind is what we want for takeoff and landing (there’s a bit more “why” involved in that, but this is the basic idea).
Entirely. I wouldn’t even bother with it until you’ve got VFR stuff down cold. Sure, we can put the flight plan into the GPS and let the autopilot fly us along, but that’s not IFR, that’s just flying in the clouds. It’s an entirely different landscape and nobody starts there in the real world, we all learn VFR first. Basic, deliberate control of the aircraft following applicable procedures. Crawl before walking 
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