can you use chandra outrage just to do the 2 damage to player
can you use it if your opponent has a hexproof creature it does no damage to that creature but it still does damage to the player
Short answer to the second thing: No, you can't, because the hexproof creature is not a legal target, and you don't target the player, that damage is just... incidental, I guess. If you want to hit an opponent, you have to be able to target a creature they control with Chandra's Outrage .
No. You can't cast a spell or activate an ability without being able to choose enough legal targets for that spell or ability (assuming it has targets).
Chandra's Outrage only targets a creature. It doesn't target a player. You can't cast it without naming a legal target, which means you can only cast it if you can target a creature with it.