Did both ones that are given on JP, and got rewards for both of them. The old one, even though it shows no rewards, grants you all rewards. (Crap though)
The second one, though very hard, gives you rewards the way you usually get them, including Legwand, 3 gems, imps, sphere frog etc
Note:It's the same as vortex FH from a while ago in JP, so it should be safe, unless you use mods.
Try to have a decent team, without damage mitigation, my team Maxwell/Leorone/Kajah/Zellha/Luther+Uda with Leorone buff got ohko'd on floor 29, and was pretty close in floor 28.
This was before the maintainence, 3 days ago to be exact, and I'm still not banned; should be safe