7th Ed. Can 2 characters fight each other without issuing challenges

[Aparach]

Can my scar vet in his unit of saurus cavalery choose to fight an enemy character in a chaos knight unit without having to challenge him? Chaos Warrior Characters are really tough one on one...

 

[Dalkarius]

He can attack the chaos knight, yes, but could not actually be one vs. one unless you declared a challenge.

 

[Aparach]

This is what I make of the rules, correct me if I'm wrong: I charge with a unit containing my champ into a exhaulted champ of khorn and I will be the one to determend if it's gona be a challenge THAT TURN. right?
The next turn he can challenge me if he whant hand if I don't dare, I must hide in the back of my troops...

 

[Craken]

You can issue the challange first yes, however if you don't your opponent can. If a challenge is accepted by either the challenge continues in subsequent turns until one of the challengers is dead.

 

[Nexus]

You can direct any/all/some attack/s at a enemy model in base to base contact with you char.

 

[Godless-Mimicry]

This is what I make of the rules, correct me if I'm wrong: I charge with a unit containing my champ into a exhaulted champ of khorn and I will be the one to determend if it's gona be a challenge THAT TURN. right?
The next turn he can challenge me if he whant hand if I don't dare, I must hide in the back of my troops...

Not necessarily, the person whose turn it is gets to declare challenges first. On rare occasions you may charge in your opponent's turn.