17FL

17FL was the 17th floor of Tower of Frozen Waves.

Stage
The stage looks like your average episode stage. There are a lot of Winged Jellies that look like it can't be collected, but can be if done properly.

Collect at least 20 Yellow Bear Jellies
Reward: 600

Simply put. There are enough Jellies to collect all the Yellow Bear Jellies. If you don't have any of these pets, Cheeseberry can help collect the unreachable Winged Jellies.

Collect at least 50 Winged Jellies
Reward: 1

Onion Fish will generate more Winged Jellies for you to collect. If you don't have Onion Fish, Cheeseberry will collect all the Winged Jellies, provided that the Pet is at Level 8. Otherwise, equip Glistening Green Leaves and a few Jellyco treasures to clear all the obstacles and safely collect the Winged Jellies.

Collect at least 1000 Coins
Reward: 3

Panda Dumpling is an excellent Pet for this, because the Coins are provided indirectly rather than directly, and you can get 300 Coins per skill activation. Be also sure to equip Shiny Golden Nunchaku and/or Uncooling Teacup's Golden Jujube Tea Bag for more Coins.

If you don't have Panda Dumpling, Magic Pod is another good strategy, but it requires precise timing with the Jellycos. The Jellyco has to land exactly on the part where the Giant Bear Jelly appears, or the Magic Pod won't spawn its second Bonus Time Jelly.