he uses sage naruto in round 2, then he used dance of impetus and he put in queue sage naruto mystery in round 2 for round 3, this way the 2 rounds cd starts from round 2, not from round 3, becuase the mystery, de facto, became not prompt and every effect may interrupt it if is used during round 2. If you don't interrupt it in round 2 the mystery goes off in round 3 and the cd goes to 1 round because 1 round passed from round 2 to round 3. Round 4 the mystery is again available.

delete, was not jigokudo XD

ah yes i forgot about it XD. So indeed works.

if he uses 1st chase and dog of hell the 8 combo started by naruto grants 100 chakra + 20 are from naruto, indeed enough to use if every round.