When is a hand considered dead?

[Hung]

Hi,

I'm the lazy type of player. Whenever I play live I just trust that the dealer is doing his/her job. I don't care much about the casino rules. Some casinos have different rules. I would like to know what the official rules is for declaring your hand as dead.

Imagine you're HU and you speak out of turn, by showing your cards. In that case your hand is not dead because you're HU and it's show down anyway. The person that was supposed to act first has the right to much or to show. But the cards are not dead. So far so good.

What happens if you're in the middle of the game in a multi way pot and you suddenly drop your cards because you're an idiot and one card ends face up on the table. If this is my home game I would allow the guy to continue but the card shows must be visible to all players.

Another situation: Imagine you're in a multi way pot and you decide to show one card to get a read. Cards dead or not?

There're plenty different situations and I would like to know the official rule. Anyone an idea?
I tried google