New Dungeon Arrived, But...

I can suddenly start from the deepest part of the dungeon, I wonder what the criteria is. What's good about this one: 1st pic: Resonance Santa fubuki added 2nd pic: Finally, various rings Dungeon 3rd pic: Some seemingly good performance drop? 4th pic: Some mismatched drop 5th pic: The dropped performance doesn't activate until equipped, so how many runs do I have to do until I can equip it? And it seems to be per style, not per character? So, can't this new dungeon be skipped? The mobs along the way are really weak, but the level 55 boss was seriously as tough as EX, I had to play carefully. And it seems pointless to bring styles you want to seriously train into the dungeon. Maybe I'll try bringing a Demon Lord next time. I really don't understand this dungeon.