Don't listen to the people complaining about the Dlc requiring you to be lvl 80. You don't, You do however need to be lvl 46 to complete all 6 arena quests. All Arenas share the lvl reqs
If you are below a certain lvl from the set arena, you will straight up do 0 dmg, not a little dmg, No damage.
46 is the lowest i could beat it at (Could be 45 for the lvl 80 difficulty)
The arenas are pretty straight forward. sand arena is challenges. Don't get hit, don't dash. ect.
Flooded city Arena is just fighting enemies.
Will update once i do the forest arena.
You can do the side quests pretty much anywhere in the story From my experience
if you beat the game and move on to doing another playthrough. 9S' Storyline
You keep the clothes in your Key items. they will not be removed.
If the arenas seem a little too hard for you, you can kill the robots that sit inside the Sand arena, exit the building with the elevator and return, they will re-spawn and you can farm EXP this way.
This is being updated as i play through the game and experience it. Will be updated/ changed if i find something that contradicts my previous statements