All those corrections can or will involve changes in the dynamics (levels) and therefore dynamics processing is virtually always involved. Secondly is "achieving a mix that approximates the original release as millions of listeners remembered it 20, 40 years ago." How people remember it years ago is relative to how they heard all music years ago, how they hear it today is relative to how they hear music today, which generally is louder! How much louder a remaster should be, comes down to a judgement call, exactly what the original master is, it's genre, what it is trying to achieve musically and what is an appropriate amount of compression.
1. If we're talking about a "final 2-channel here" then a limiter cannot make "a back-up vocalist subjectively half as loud as the lead vocalist, almost as loud as that lead" and neither can a compressor! A compressor cannot do this for exactly the same reason as a limiter can't, because essentially they are exactly the same thing!
2. That's all true BUT it's all true of a compressor as well because they are the same thing. If you're going to say that a compressor can act on the vocals, that would be true but it would be equally of true of a limiter. A limiter is the same as a compressor, the only difference is that a limiter compresses to a limit whereas a compressor doesn't, unless it's ratio is set to infintity:1 with a very short attack time, in which case our compressor is now a limiter!
3. Yes it is entering into limiting territory but it depends on where the threshold is set and the input signal it is fed. I'm not sure you understood what I stated earlier about compressor settings? Let's use your example song again, ff the input signal goes up to say 0dBFS then with a 10:1 ratio and limit set to -40dB the output signal would be -36dB, it won't have actually limited to -40dB and therefore it's not actually a limiter! If however we set it much more sensibly, say -6dB then with a 10:1 ratio our output will indeed be -6dB (or a decimal point or so above), it is now a Limiter! And obviously (hopefully!), if we fed that same -6dB signal into a compressor (with a suitably short attack time and a 10:1 ratio) our compressor would also limit to -6dB and therefore is now a Limiter! A ratio of 10:1 under most usual conditions is enough to be a limiter but to be certain it's ALWAYS a limiter then the ratio has to be infinity:1.
G