I have a question about an implementation detail - when are old blocks verified by each full node? I.e. when will I be "caught" if I change the contents of an old block (and thus break the hash chain)
From what I've seen, the possible answers include: when it's downloaded and when you do a -rescan.
However, does a full node regularly verify the integrity of the chain from start to finish?
(I'm aware that changing the history on my node doesn't do any good, as those verifying my future transactions will have the correct chain and thus refuse any attempts to double spend)