Rules questions

Hey guys, 2nd day playing and having many questions, please help!

• Can you Knockout a stage card? What if is rested?

• Effects like [Activate:main] can be activated more then once? So in every main phase?

• Do the effect from [when attacking] activates before the counter phase?

• Can you use a character as a blocker when the card is rested?

• When you have a card that rest don of your enemy and you do it in your turn, will that don be rested for one rivals turn or be activated?