Basically those coins are only dead when code is gone or not publicly available. As long as the code is available the coin can be overtaken by a new developer to revive it.
This has already happened a lot of times. You just need some interesting people including a good developer to revive a coin and bring it back to live. Anyway, this is a nice list you posted.
Yes, that's true.
One just needs a group of people including developers to 'revive' a coin.
So coins are theoretically never dead. They are just dead if the source code gets lost.
That's really a good thing about the crypto space. You can always bring a coin back to life if developers abandon it.