The meaning is strange when you ask if you know a book or toy... It sounds like "are you acquainted with this book?" which is just weird. It's not something that would be said too often. "Do you know about" is better, but still, "to know" is not often used with objects.
As for the two sentences that you asked about, both are correct, and they both have the same meaning, too.
I tried to find a proper grammar rule on adverb placement, and the best one I could find is:
Adverb position varies greatly in English. However as a general rule, adverbs of frequency come before the main verb. (except when the main verb is the verb to be)
So, according to this rule, "I would have never said that." is the "right" sentence.
The correct form is I would never have said that. The past perfect form of the verb "to say" is "have said"
know this book know about this book know of this book All are correct grammar but subtly different. The first suggests thorough knowledge, as there are no extra words to distract from KNOW The second makes it clear that you are not expecting t