> Canned food: if hermetic seal is intact, it's edible.

Definitely not a universal truth. Canned food can develop botulism, you do not want to mess with it. Any cans that are bulged or show signs of swelling should be discarded - don't even risk opening them.

There are guys on YouTube who explore old army rations (which were basically all canned food prior to the 1980s), and when they decide to open a bulged can "for science" they will often literally break out a gas mask. That said, it's also not terribly uncommon for them to find rations dating back to WW2 and older that are still partially edible.