Heaton and Stocks say that "can know" is seldom used, which means that sometimes it's possible.
A sentence like "We can know all about India in our geography lesson" sounds unnatural because we never normally have to express the idea that somebody has the ability to possess information about India. Either you know about India, or you don't. What is needed here is a more active verb, like "learn": "We can learn about..." means we have the opportunity to find out about India, and that's more useful.
The three sentences you have found are rather different. I'm not sure the 3rd sentence was written by a native speaker, though, as it sounds very unnatural to me.
But in sentences 1 and 2, "know" has a different meaning: it means "become acquainted with" or "experience"; and "can" in each case means "have the opportunity to". This construction is a little old-fashioned, and so you'll often see it, as here, in religious contexts.
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