It's special skill named foam/wace which give a chan
ce of extra turn. Perhaps what percentage of chance is it? Is there really possibility it gives extra chance in single fight/battle?

That question proceeds to another question, if percentage is high and likely to trigger in a fight, who will I empower first? High Reign Dragon with A+ stats or High Commander which I newly obtained. Thanks

I don't know for sure but I think it's about a 50% chance of giving a second turn. It will never give a second turn if the dragon you're fighting dies. So if you knock it out with Wave or Foam you don't get a second shot.

The High Commander can also be trained so it has both Wave and Foam if you give up either the Nature, Light, or Metal attack. That's what I did with mine. Now he sometimes hits 3 times without a return attack making him currently my most powerful dragon.