Also: those three are VERY distinct. When you use "opinion" it can mean either; that doesn't mean it means ALL OF THEM AT THE SAME TIME.
That's precisely my point: you're using it in a way that doesn't fit the context. You can't use "belief stronger than impression and less strong than positive knowledge" the same way as you use "a view, judgment, or appraisal formed in the mind about a particular matter" or "a formal expression of judgment or advice by an expert". That's WHY the dictionary lists them separately. Context gives you a clue about which one is used when.
And there's other dictionaries, too, which explain the word differently. That's... how language and dictionaries work.
Nobody is redefining anything. I'm explaining that you need to be careful what you're talking about when you use "opinion" because it means different things depending on context - YOUR dictionary quote PROVES that much.
That's my point, though. You're using it IN MULTIPLE WAYS but those are not MUTUALLY EXCHANGABLE. You can't just use the first definition THE SAME WAY you use the second or third, and so on. That's WHY THEY'RE SEPARATELY LISTED IN THE DICTIONARY.
As much as we can for any historical figure, sure it would. As much as we proved, say, Tutankhamun's remains were Tutankhamun. To the degree that we could be physically certain, it is - at least in principle - possible to do the same for Jesus. Remember, we're talking about a theoretical possibility here; not about the LIKELIHOOD of that actually happening, but about whether or not the laws of nature would preclude it or not (like they do for my example).
Which part of "it can't be solved therefore it's safe to ignore and move on" is deep and profound to you? Seems about as quick and shallow as it can get to me.
Yes, but that's a different kind of "opinion" than "I just believe it, no need to explain". You already agree, because you're talking about COMING TO CONCLUSIONS - that's fundamentally different from "I just believe it", which is ALSO what "opinion" can mean.
My whole point is that you can't use one like the other, and pretend that opinion="the sum of my positions on a subject" IS THE SAME OR CAN BE USED THE SAME as opinion="a subjective preference I hold without needing to explain or prove it". Because one is really just an argument (or a sum of arguments); and the other IS NOT, and can't be used like one.
Conflating them is a massive category error.