One thing that's worth remembering is that, for the most part, historians don't disagree about the historical record (that is, evidence about the past that has survived to the present) itself, at least not without very good reason to do so. That means that we can point to a great deal of established truth in the past - unless we doubt the basis of large chunks of historical evidence, for instance, we can all accept the fact that the Allies invaded Normandy on June 6, 1944. This can be where the line between historical debate and denialism tends to lie - denialism involves negating large swathes of the historical record to make its claims. It is this negation that earns the ire of historians, who are simulatenously happy to argue all day long about interpretating that same body of evidence.

Most historical writing, however, is not concerned with establishing or questioning basic truths. That's partly because we don't tend to need to write books 'proving' the Allies invaded Normandy (what's the point?), and partly because it's boring. A lot of the interest in history lies elsewhere than this basic framework of agreed-upon events - we like to focus on the whys and hows, not the whats, because the whys and hows ultimately matter more. The fact that Normandy was invaded doesn't tell us a lot of stuff we want to know about the past. This is where interpretation comes in - we can disagree on why Normandy was invaded or what it was like for those involved, putting forward competing explanations based on the same historical record that establishes without a doubt that the invasion itself took place.

If you'll permit a long, tortured analogy, let's think of things in terms of breakfast. Let's say you had cereal for breakfast today. We know this for certain, because you wrote in down in your journal, have a half-empty cereal box in your cupboard, and an analysis of your faeces the next day revealed telltale traces of the substance in question. Above all, perhaps, we know because we asked you and you don't really have a reason to lie. The historical record points, with a great deal of certainty, to the fact that cereal was consumed.

But this fact by itself doesn't tell us a great deal about the past. Why did you eat cereal? Did you see an ad for cereal the evening before on television, planting the idea in your head, revealing that you live in thrall to consumerism? Or is this eco-cereal, sustainably grown and packaged, that indicates that you're worried about the cost of industrialisation on the planet? Does the fact that you ate cheap cereal for breakfast indicate that your socio-economic status is rather low, an exploited cog in a brutal capitalistic machine? Or, conversely, were you eating fancy, boutique cereal, a sign of your wealth and sophistication? What does cereal mean to you, anyway? Does cereal remind you of your childhood, the last time you were ever, truly happy, your forlorn attempt to recapture the safety and security of youth? Is cereal a status symbol, that impresses your breakfast companion? Is cereal part of a routine, a way of grounding yourself in an ever more chaotic world? Do you eat cereal without added sugar, because you're worried about your weight and health? Does it contain extra fibre, because some weird historians asked you to provide a stool sample for them, and you haven't been that regular lately?

All of the above, arguably, might tell us more about you as a person or the society you live in than the mere fact you ate cereal for breakfast, yet are all matters of interpretation of the same body of evidence. What changes is the questions asked of that evidence, and the uses to which it is put. The result is a series of potential truths about the past - some contradictory, others reconcileable, but all stemming from an agreed-upon truth that you did in fact eat cereal for breakfast today.

I'm afraid I'm not sure I understand the question here, unless you've got some specific (and quite highly demanding) theory of knowledge in mind or something like that. In particular, I'm not sure what you mean when you say...

Can we even refer to the facts or events of the past as the knowledge, when it is so volatile and could be changed any time

I would have thought it was obvious that past events are precisely those that cannot be changed (owing to their already having happened). So presumably you mean, rather, to say that we sometimes learn new things about what happened in the past? Fair enough, I suppose, but I've no idea how that is meant to generalize to the skeptical claim that we do not have knowledge of the past. We also learn new things all the time about the future, about particles, about the human body, about animals, and so on and so forth. But I presume you'd be willing to admit we have knowledge with respect to all those things nevertheless, no? So the mere fact that we sometimes learn new things, get new evidence, and all that good stuff surely doesn't mean we can't speak of knowing (for example) that Caesar defeated Pompey.

Is the thought perhaps that new evidence in history sometimes leads to the wholesale overthrow or revision of older theories? That is true enough, though on the whole considerably rarer than one might suppose. But again, this sort of thing happens outside history as well. Newton and Einstein are perhaps the most famous example, but we might also cite other examples from various STEM fields... the abandonment of Euclid's parallel line postulate in geometry and Russell's realization that the naive comprehension axiom in set theory could not be maintained on pain of contradiction both leap to mind straight away. Other, more run of the mill cases might be any experiment that is performed that necessitates a revision to a physical theory. This seems to me pretty straightforwardly comparable (in the relevant epistemic senses) to finding some new bit of evidence that forces a revision to a historical theory. So, again, I fail to see a decisive objection to speaking of knowledge in history in particular here.

Maybe the meat of your worry hangs on this interpretation business? Now here, I think it is worth pointing out that while interpretations are up for dispute, they are not arbitrary. Older works in history are often spoken of disparagingly for being biased in various ways or for over-emphasizing the importance of great men and women (usually men though). But the dispute here is that (i) these past historians were letting some of their own bias seep into their work, an objectionable practice in any field, and (ii) ignoring other important aspects of the past and sources of evidence. But it is not as though these past historians were speaking nonsense either. The structures of power that come to the fore in such works are an important aspect of the past that bears thorough examination. What the rich and powerful men in positions of power said and did are of course important aspects of the past that demand academic study. Part of why that is done less nowadays by academic historians is that a lot of work has been done in those areas, whereas other areas have been relatively neglected. There are far more studies of Thomas Jefferson than there are of the life of the common farmer in Virginia. But it is not as though any of this is divorced from reality. There is a common body of fact and evidence and uncontroversial truths upon which interpretations are based. The differences in these interpretations often enough spring from which bodies of evidence one happens to engage with. But presumably, all such interpretations are advancing our knowledge of the past in various ways; they are all, as it were, driving at the truth, even if they are driving at it from different directions or different starting points.

All that aside, I still don't see that this is going to get you an epistemic distinction of the right sort between history and other fields. Yes, there are plenty of academic debates in the study of history, of the best way to piece together various sorts of evidence and what new sources of evidence bear looking at. But, again, I don't see that this suffices to motivate any broad skepticism about history any more than academic debates in literally any other field do. This is especially obvious with respect to the uncontroversial truths upon which such debates are founded. To wit: That historians dispute the best way to understand Roman religion neither implies that there is no right answer nor that we do not know anything whatever about Roman religion. We know all sorts of things about Roman religion. Here is an example: There was a religious office called Pontifex Maximus, an office that was held by, among others, Augustus. What we lack is a full, comprehensive, and total knowledge and understanding of Roman religion. But that is not so bad. We also don't have total knowledge of the Sun, or of the integers, or of the ocean floor, or... You get the idea.