1. As far as I understand, if Courageous Soul attacks, he will grant all the other 'friendly' champions +2 offence in the subsequent attacks (and not necessary those champions which attack with Courageous Soul), is this correct?Correct.
2. What happened if Courageous Soul attacks and then he is subsequently removed from the board, will all the other champions continue to receive the boost of +2 Offence?Correct.
But the answer to the question you did not ask is this:
If Champions enter play after Courageous Soul has attacked, they do not benefit from the +2. It only affects Champions who are in play when he attacked.
3. If champions are broken and then the player is required to replace it with human/demon/zombie/wolf tokens, what state will those tokens be in when it come into play? For example, I have expended Gold Dragon to attack and then my opponent play Inner Demon to target Gold Dragon, will the token come into play expended due to state the Gold Dragon is in or will it come into play deployed as a 'fresh' champion.They come in to play Prepared. They are new and different Champions.