Hello!

About your question, what he said above is correct. And for your other question, yes we have a list of ninjas with breakthroughs and skill trials, it was made by one of our Forum Moderators. I will send it to you via Private Message. Thank you.

Hello!

Okay, hmmm. Let's say you got Gakido's Mystery+2 (Yellow Breakthrough). From there, you can change it to his Mystery Y+1 (Yellow Trial). Check the image below.

And you can revert it back to +2 whenever you wanted. But, let's say you have +2 and you want to change it to a Blue Y skill only, then yes, it will happen but you cannot go back to Yellow + Series Skill Breakthrough and you have to spend fragments again or vials. It's kind of like, you degraded it.

In short, Yellow + Rarity can be switched to Yellow Y/L Rarity, back and forth. Yellow Rarity to Blue Rarity is possible but the skill will be degraded and will be unable to go back to Yellow again. Blue + Rarity can be switched to Blue Y Rarity and vice versa. Blue to Yellow is simply not possible.

I'm not sure if I explained it well but I hope it will help you xD ..