Is it simultaneous, like 1st me > several tied 2nd places? Or is there a sequence to it. I know 802.6. Combat damage is assigned in APNAP order. Other than that, the combat damage step proceeds just as in a two-player game. See rule 510, “Combat Damage Step.” under "Attack multiple players" is a thing, but does that just mean that turn player deals all his damage first, or is there a sequence to the order in which players lose to lethal damage?
All combat damage happens simultaneously.
510.2. Second, all combat damage that’s been assigned is dealt simultaneously. This turn-based action doesn’t use the stack. No player has the chance to cast spells or activate abilities between the time combat damage is assigned and the time it’s dealt.
802.6 is simply explaining a slight difference to 510.1:
510.1. First, the active player announces how each attacking creature assigns its combat damage, then the defending player announces how each blocking creature assigns its combat damage. This turn-based action doesn’t use the stack.
So "defending player" in this case means each of the opponents being attacked, in APNAP order.
However, the premise of your question may be flawed. There is no "second place" in magic. It doesn't matter which player loses first, or if it is simultaneous. If I kill opponent A on turn 5, and then kill opponent B on turn 6, opponent B isn't "second place" while opponent A is "third place". They are simply both players who did not win the game.