1. Yes
Of course it is; we are playing a tabletop role-playing game and the players can only make intelligent choices if the meta-constructs of the mechanics have some perceptible in-world difference from one another.
To think otherwise makes the game impossible to play.
2. No
Of course it isn't; we are playing a tabletop role-playing game and the players can only perceive what their characters can perceive. When you Dodge you "focus entirely on avoiding attacks", which is a purely internal situation and is not differentiable from other actions that don't require you to do anything until the world impinges on you, such as Disengage or Ready.
To think otherwise makes the game impossible to play.
Both answers are right
... and they sit at the ends of a continuum of equally right answers between concealment and revelation.
Whatever is the agreed-upon situation at your table is 100% correct. It would be nice if this was agreed up front, but when you have players with mismatched expectations, they generally don't know they are mismatched until something like this happens. When it does happen, deal with it and move on.
Just be consistent - what works for the monsters works for the players.